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DRPHIL914
I have been dealing with this for 12 years, a non-running defrost fan. i even pulled this out 2 years ago and rebuilt it with new flapper seals and main body seal then made sure fan turned but didnt bench test the motor or resisitors, so as a result it still does not work properly. i will be documenting this because 914rubber and Mark will soon be putting together a kit for this that includes all the hardware seals and even a motor i believe, BUT i still have problems and questions!!! so i am starting this thread to get information on diagnosing the common causes of it not working and how to fix it, and then document the rebuild and replacement of the motor, fan, resistor and maybe the control unit in dash. Others have documented the reinstallation of the fan and the cables so i will not duplicate that. and we may want to link other threads hear that have done that as well.
Mark is sending me a kit soon, so while i wait for it, i will have to get some more information about the wiring and resistors function and how to test them .

I had this out last week and tested 3 different control units due to thinking that my issue was a control issue, because it runs on one speed, #2, and anything else does not work and it will then throw the fuse. most assume this would be caused by bad slider unit but i tested 3 of them and 2 are like new with no wear on the sliders , still same result. so i am suspecting the resistors /plug aparatus .
If anyone has done this and cares to share how to examine and test that for proper function, lets start there.


Resistor function, which lead is which and examination of the control units
I will take pictures of mine tonight and post those soon. once this figured out and fixed i will do a full step bystep on reassembly too.

Looking for lots of help and input on this, thanks!!!

Dr. Phil
Superhawk996
Not trying to be a jerk here. But I keep seeing a pattern in the forum when people are stuggling with electrical issues.

Rule #1: Don't assume anything

Rule #2: You MUST have a schematic and understand how to read and use it.

Rule #3: You must have a DMM

Rule #4: Learn the 1/2 split method (Google or PM me)

Rule #5: You must follow a methodical approach.

If you're not already familiar with DC motor theory, spend some time on Google to understand that too.

Chasing other people's assumptions of what might be the cause and/or fixes that once worked for so and so will lead you on a path to nowhere.
DRPHIL914
QUOTE(Superhawk996 @ Jan 21 2021, 10:43 AM) *

Not trying to be a jerk here. But I keep seeing a pattern in the forum when people are stuggling with electrical issues.

Rule #1: Don't assume anything

Rule #2: You MUST have a schematic and understand how to read and use it.

Rule #3: You must have a DMM

Rule #4: Learn the 1/2 split method (Google or PM me)

Rule #5: You must follow a methodical approach.

If you're not already familiar with DC motor theory, spend some time on Google to understand that too.

Chasing other people's assumptions of what might be the cause and/or fixes that once worked for so and so will lead you on a path to nowhere.


soooo maybe you've missed the main thrust of this , which is to document a rebuild process, but also the trouble shooting and diagnosis of the common causes of failure of this unit., mainly for those with less experience in working with electrical issues.
1- nothing here has been or is assumed
2- i have the schematics on the laminated sheets - most have never had any electronics or wiring classes, i have ha some but many years ago
4 - i always search the forum and google for same or similar topic, and have done so regarding this extensively , only one thread comes up with any explanation of the resistor connections by @beatnavy and that does not really look into testing or replacing the resistors
5- thats the plan

regarding my own current situation ive verified power to the source, proper ground, and just a basic trial and error experiment found the change of controllers made no change. so i could have 3 controllers that all have exactly the same issue OR more likely the issue is at the fan and resistors.

SO have you sir gone thru this process with this unit? if you have do you have some constructive advice or experience specifically regarding it? if so please post.
since i am not an electrician i may also be asking how to interpret the schematic.
but yes i agree your list of the above suggestions is not a bad , yes you kind of do come across as a bit of a jerk , sorry, if that is all you are contributing here.
with that said i am no rookie here having essentially taken this car apart and put tit back together in the past 12 years, and how did i do that? with a lot of time and energy in research and internet searching and a lot of stupid questions getting valuable answers here on this forum. I would never have started this post if there were already a nice clear concise description on the subject (its not just the electrical issue as i stated in my first post but also to document the rebuild)


BeatNavy
Phil, if it runs on one speed but not another (or the other two), it's likely a blown resistor. Too much resistance builds up through the ground circuit and it fries. I remember shortly after putting mine back in after cleaning it up -- I put it on low speed and saw a little puff of smoke came up through the vent grill. IIRC it uses three resistors in different combinations to control the effective voltage supplied to the motor. I have a fresh resistor pack that BillC sold me a few months ago. I'll see if I can find that for reference (although doing this wasn't high on my priority list, so I may have buried it with my other parts that I'll get to "one day.")
DRPHIL914
QUOTE(BeatNavy @ Jan 21 2021, 12:41 PM) *

Phil, if it runs on one speed but not another (or the other two), it's likely a blown resistor. Too much resistance builds up through the ground circuit and it fries. I remember shortly after putting mine back in after cleaning it up -- I put it on low speed and saw a little puff of smoke came up through the vent grill. IIRC it uses three resistors in different combinations to control the effective voltage supplied to the motor. I have a fresh resistor pack that BillC sold me a few months ago. I'll see if I can find that for reference (although doing this wasn't high on my priority list, so I may have buried it with my other parts that I'll get to "one day.")


thats kind of what i figured, i found your thread from a couple years ago, you were working thru your issue and had figured out which wire was what. I have 2 other fan boxes and i hope i have one good resistor pack , because i have tried looking and have not found any out there id dont think they can be bought anymore.

i might post a WTB ad on classifieds here as well.
thanks for the input!

Phil
mepstein
Just like starter motors and alternator, the climate control motors can be rebuilt. Usually cheaper than new and often better built. Plus you know the fit and specs are exact.
framos914
I went through this a few months ago. Since I had the gas tank out, I thought I would tackle the non working defrost fan. I removed the fan for bench testing.

I checked resistance between the hot pin on the unit and each of the other 3 pins. I did get 3 different resistance values (should have noted the resistance values).

Next I connected 12 volts to the unit and applied ground to each of the other 3 pins. I got the 3 different speeds.

I turned my attention to the control lever. Since none of the 3 speeds worked I concentrated on the part of the slider contacts that was common to all 3 wires. Must have just been corroded because after a good cleaning of all contact surfaces the fan worked normal.

I removed, cleaned and lubed the windshield wiper assembly while I was in there. Of course it was a PITA reinstalling the fan. Ian has a good video on how to install fan.
Superhawk996
I'm here to help. Not trying to be a jerk. Apologize if it's coming off that way, I'm an engineer so it comes naturally. laugh.gif


https://www.youtube.com/watch?v=9LaV8lSdOHQ


I have a copy of Prospero's garage laminated schematic. Nice for some things like color codes but sucks for others. Not sure if this is what you have. For the ventillation fan work, it is closer to sucks. The fresh air fan has no component detail on what in there, only a block diagram.

Haynes manual is better IHMO.

@bbrock recently tore into his resistor pack. I can't seem to find the thread at the moment.

There are two wire coil resistors. They control Low and medium. High is wired w/o a resistor to motor per Haynes (white wire) . There is also a bi-metallic thermal cut out switch per the Haynes schematic. The resistors and thermal cutout switches can be verified with DMM.

Unfortunately the Haynes manual isn't clear on how the bimetallic switch is physcially built. Brent's photo's I think had detail. The Haynes manual does show that if the switch is closed, it bypasses the resitor, drives the fan at full speed, and then cools off the wire resistor coil, at which point the bimetallic switch should open again and slow the fan to proper speed.

With respect to the control levers, have you verified the connections and continuity with DMM? "so i could have 3 controllers that all have exactly the same issue OR more likely the issue is at the fan and resistors"

As you state, you could have 3 bad units (not likely) but a quick continuity and/or resistance test with a DMM will verify them and remove any doubt. That is sort of what I was implying by making assumptions. Don't assume that and/or jump to conclusion is at the fan and resistors. Not trying to beat you up on this. It's a very common thing to do that can lead you astray and lot's of people make these sort of inferences when trying to do electical work. Comment above from @framos914 is spot on as we was basically using a half split method either knowingly or by intuition.

The reason I mention DC motor theory is because if you have a motor that isn't free to spin (bad bearings/bushing) it will draw more current than it should and could blow the fuse and/or not even rotate on the lower speed. Likewise, if you have shorted windings in the motor, it could blow fuses. We can verify each of these possibilities in a methodical way. But, let's not get ahead of it yet.
BeatNavy
So I found the resistor pack. And I found my old photos. Looking at the resistor pack I acquired I can now see values on there that I never noticed before. There are two resistors. The one on top is 2.5 ohms and the one in bottom is .75 ohms. So there are three settings. I'm assuming high speed runs through neither resistor, medium through one (maybe the .75 ohm resistor), and low through both for 3.25 ohms of resistance. Probably 50 watt at least.

Click to view attachment

Edit: And to Superhawk's point, when I managed to get my motor spinning, I never really fully rebuilt it, so it probably wasn't spinning as freely as is should. That means more power draw through that resistor at low speed than it was designed for, and blowup.gif
Superhawk996
I'm also going to throw another one out there. You didn't mention which fuse was blowing.

Is it pulling power from the proper fuse? Should be fuse #8 - 25A fuse.
Superhawk996
page 72 post #1439

Click to view attachment

http://www.914world.com/bbs2/index.php?sho...290&st=1420

Here is the detail on the bi-metallic switch BELOW the resistor.

@bbrock problem was only two speeds. Fully acknowlege this is different than your problem but it does detail how the switches are physcially built if you wish to document this thoroughly.
BeatNavy
Ahhh...ok, that filled in at least some of the missing pieces for me. I think I have a better idea how this thing works.

Amazing how complicated it is and how much engineering went in to this little bugger.
Superhawk996
Here's a few links about the 1/2 split method. This is method of troubleshooting that was taught to me by USAF as the quickest way to troubleshoot electrical equipment. It works. More than happy to elaborate if I can assist. Unfortunately words aren't the best way to describe the process but at the same time I haven't found a great video yet.

I've posted these intermittently in other threads where people are troubleshooting electical systems and some have PM'd me that they found them to be helpful.

https://www.ecmweb.com/maintenance-repair-o...f-halfsplitting

https://rule11.tech/troubleshooting-half-split/

https://artoftroubleshooting.com/2013/04/25...ear-up-to-here/
Superhawk996
QUOTE(BeatNavy @ Jan 21 2021, 02:50 PM) *


Amazing how complicated it is and how much engineering went in to this little bugger.


Yup, typical German part!
914_teener
Glad you guys are getting along.


I did this years ago....twice. Fixed the fan and then the wiper motor gave up the ghost.

Sage advice:

Don't do one without checking the other. The only way to replace the wiper motor is by taking back out the fresh air box and then fan...and then wiper assembly.

Turns out when the OP turned on the fan after it filled up with leaves it burned out the resister and overloaded the wire harness burning it and then shorting to the wiper part of the harness.......


Taking this out twice and tracing down the short and in that process I believe new expletives were invented.

So.....test both while your there.
DRPHIL914
QUOTE(Superhawk996 @ Jan 21 2021, 01:29 PM) *

I'm here to help. Not trying to be a jerk. Apologize if it's coming off that way, I'm an engineer so it comes naturally. laugh.gif


https://www.youtube.com/watch?v=9LaV8lSdOHQ


I have a copy of Prospero's garage laminated schematic. Nice for some things like color codes but sucks for others. Not sure if this is what you have. For the ventillation fan work, it is closer to sucks. The fresh air fan has no component detail on what in there, only a block diagram.

Haynes manual is better IHMO.

@bbrock recently tore into his resistor pack. I can't seem to find the thread at the moment.

There are two wire coil resistors. They control Low and medium. High is wired w/o a resistor to motor per Haynes (white wire) . There is also a bi-metallic thermal cut out switch per the Haynes schematic. The resistors and thermal cutout switches can be verified with DMM.

Unfortunately the Haynes manual isn't clear on how the bimetallic switch is physcially built. Brent's photo's I think had detail. The Haynes manual does show that if the switch is closed, it bypasses the resitor, drives the fan at full speed, and then cools off the wire resistor coil, at which point the bimetallic switch should open again and slow the fan to proper speed.

With respect to the control levers, have you verified the connections and continuity with DMM? "so i could have 3 controllers that all have exactly the same issue OR more likely the issue is at the fan and resistors"

As you state, you could have 3 bad units (not likely) but a quick continuity and/or resistance test with a DMM will verify them and remove any doubt. That is sort of what I was implying by making assumptions. Don't assume that and/or jump to conclusion is at the fan and resistors. Not trying to beat you up on this. It's a very common thing to do that can lead you astray and lot's of people make these sort of inferences when trying to do electical work. Comment above from @framos914 is spot on as we was basically using a half split method either knowingly or by intuition.

The reason I mention DC motor theory is because if you have a motor that isn't free to spin (bad bearings/bushing) it will draw more current than it should and could blow the fuse and/or not even rotate on the lower speed. Likewise, if you have shorted windings in the motor, it could blow fuses. We can verify each of these possibilities in a methodical way. But, let's not get ahead of it yet.
QUOTE(Superhawk996 @ Jan 21 2021, 02:11 PM) *

I'm also going to throw another one out there. You didn't mention which fuse was blowing.

Is it pulling power from the proper fuse? Should be fuse #8 - 25A fuse.
QUOTE(Superhawk996 @ Jan 21 2021, 02:22 PM) *

page 72 post #1439

Click to view attachment

http://www.914world.com/bbs2/index.php?sho...290&st=1420

Here is the detail on the bi-metallic switch BELOW the resistor.

@bbrock problem was only two speeds. Fully acknowlege this is different than your problem but it does detail how the switches are physcially built if you wish to document this thoroughly.



aktion035.gif hey its all good, sometimes things come across different in print, but really no offense taken, i can see that engineering mind go to work! my son and my nephew are both engineers, my electrons choose the path of least resistance av-943.gif and went with the spinal biomechanical engineering( chiropractor) but really got into the functional biomechanics, always loved learning how everyting works , still learning and digging in on this stuff, but i digress---
- thanks for pointing out the continuity on the controller i will recheck that and compare the other units , i did that a few years ago so will recheck and document it.
- i have a free turning fan, that seems good on this unit , not my spare unit.
- mark and Matt are thinking similar in rebuilding the motor, new ones Bosch are $80 or so, not expensive, but not cheap either.
-i need to check but pretty sure its fuse #8 being blown
if its not that means someone has been messing around. I went thru the whole harness and fuse box when i installed the new box with blade fuses a few years ago. but again i need to not assume but re-verify.
then need to measure the resistance of these 3 circuits on each unit i have.
I wonder if the spring in essence is your resistor but is broken and we know the needed value, should be able to rebuild that i would think right?
first things first.

BTW @Superhawk996 - have read all your build thread since it started, you also have mad fab skills, wish i had the room for doing that kind of work, i had to outsource mine but that ended up being worth at the time, you know time vs money and i dont have a lot of either but still working so thats the way it went.

lots of great infor hear already, will get at measuring and checking on these items and get back here soon.

Phil
Superhawk996
QUOTE(DRPHIL914 @ Jan 21 2021, 05:34 PM) *


I wonder if the spring in essence is your resistor but is broken and we know the needed value, should be able to rebuild that i would think right?



@DRPHIL914 Thank you for the kind words regarding the rebuild of my stromberg.gif!

Just for clarity, it isn't a spring per se. It is basically a wire wound resistor without a housing just suspended in air. The resistive coil is exposed to air flow and is air cooled (like the engine). Pretty neat huh?

If the coils were touching one another, resistance would decrease. If it breaks or goes Poof and opens up, now you have infinite resistance. Either of these scenarios can be checked with a DMM.

In @BeatNavy 's case, if he had a stalled motor (or very slow spinning motor), the low speed resistive element probably got too hot both from too much current draw (from the stalled motor) and lack of cooling from no airflow and then the smoke got out. hissyfit.gif

Not so simple to repair but not impossible in concept.

The resistive wire is a special alloy designed both for stable resistance per unit of length as well as good thermal properties (doesn't melt easily, stable resistance at various temperatures, etc.).

Here is the Wiki on what it could be.

https://en.wikipedia.org/wiki/Resistance_wire

Nichrome and Magnanin are the most common.

Much easier to find a donor and replace if it turns out to be a resistor.

If I had to McGyver something, I'd start looking at toasters for their resistive elements but that would take some real trial and error to understand if it could even be done. huh.gif sheeplove.gif More seriously speaking, I'd start looking to other more readily avilable domestic blower motors to see if I could find a similar wire resistive element and would cobble that. Alternatively, you could replace the resistor with say 12 gauge copper wire (zero ohms resistance) and you would esentially have two HIGH speeds. Or I guess, you could just bend the bi-metallic switch contact to be closed all the time. Same result - bypasses the resistor. That was what caused @bbrock 's problem.

With a little math we could roll (i.e. wind) our own. smoke.gif

https://www.amazon.com/Nichrome-80-Gauge-Re...F9N7AHK43ZF4CP8

Many thanks to Brent for photographing and documenting that bugger!
bbrock
@Superhawk996 I can't believe you were able to dig that out of my thread. I had forgotten all about it. And yes, my problem was that my blower switch positions went low, high, high. So the blower worked in all positions, but medium speed was missing as it was going straight to high because of that little breaker gizmo.

As for repairing a blown resistor - how important do you suppose it is to use an open coil resistor. Would something like this work as a replacement?

IPB Image

https://www.digikey.com/en/products/detail/...A502R5J/2366322

It's funny. I have a roll of nichrome wire left over from a failed attempt to build a DIY plexiglass bender many years ago. I remember when I was trouble shooting my blower that I might finally get to use that wire to wind a new resistor. Alas, it was not to be...
DRPHIL914
QUOTE(Superhawk996 @ Jan 21 2021, 06:01 PM) *

QUOTE(DRPHIL914 @ Jan 21 2021, 05:34 PM) *


I wonder if the spring in essence is your resistor but is broken and we know the needed value, should be able to rebuild that i would think right?



@DRPHIL914 Thank you for the kind words regarding the rebuild of my stromberg.gif!

Just for clarity, it isn't a spring per se. It is basically a wire wound resistor without a housing just suspended in air. The resistive coil is exposed to air flow and is air cooled (like the engine). Pretty neat huh?

If the coils were touching one another, resistance would decrease. If it breaks or goes Poof and opens up, now you have infinite resistance. Either of these scenarios can be checked with a DMM.

In @BeatNavy 's case, if he had a stalled motor (or very slow spinning motor), the low speed resistive element probably got too hot both from too much current draw (from the stalled motor) and lack of cooling from no airflow and then the smoke got out. hissyfit.gif

Not so simple to repair but not impossible in concept.

The resistive wire is a special alloy designed both for stable resistance per unit of length as well as good thermal properties (doesn't melt easily, stable resistance at various temperatures, etc.).

Here is the Wiki on what it could be.

https://en.wikipedia.org/wiki/Resistance_wire

Nichrome and Magnanin are the most common.

Much easier to find a donor and replace if it turns out to be a resistor.

If I had to McGyver something, I'd start looking at toasters for their resistive elements but that would take some real trial and error to understand if it could even be done. huh.gif sheeplove.gif More seriously speaking, I'd start looking to other more readily avilable domestic blower motors to see if I could find a similar wire resistive element and would cobble that. Alternatively, you could replace the resistor with say 12 gauge copper wire (zero ohms resistance) and you would esentially have two HIGH speeds. Or I guess, you could just bend the bi-metallic switch contact to be closed all the time. Same result - bypasses the resistor. That was what caused @bbrock 's problem.

With a little math we could roll (i.e. wind) our own. smoke.gif

https://www.amazon.com/Nichrome-80-Gauge-Re...F9N7AHK43ZF4CP8

Many thanks to Brent for photographing and documenting that bugger!

thanks for explanation, it’s fascinating, it is “cool” , and actually amazing how they worked all that out.
all fast would be better than none at all , i need to test mine this weekend so i know what i am looking at.

Superhawk996
QUOTE(bbrock @ Jan 21 2021, 09:31 PM) *


As for repairing a blown resistor - how important do you suppose it is to use an open coil resistor. Would something like this work as a replacement?

https://www.digikey.com/en/products/detail/...A502R5J/2366322




It would definately work in the sense of functionality.

I think the reason for the open coil resistors is available package space and better cooling.

Looking at the size of the linked resistor, 2"L x 1"W and about the same 1" tall, I don't think it would fit. Could it have leads soldered to the resistor and then soldered to the OEM resistor holder and then mount the thing somewhere? Probably. I would be concerned about potential for the resistor to get hot enough to melt or deform plastic at 50W if JB welded to the housing or something like that. Drill holes for wires to exit the fan housing and mount that style resistor to the body as heat sink? screwy.gif Sure, depends on how bad you really need a low or medium speed. laugh.gif

The key thing I don't know is how much current is the fan pulling at start up (peak in-rush) and what is is steady state operating current. Once we know that, we could properly size the resistors. 50W might be overkill? confused24.gif

Maybe this weekend I'll go over to storage and retrieve my fresh air box. I know mine worked on at least one speed before I tore the car down. Might be a good time to check out my own motor and resistor pack too. I'm hoping to drive this stromberg.gif by Fall so it wouldn't hurt to know my fan is up to snuff. rolleyes.gif

Could measure my fan for operating current. But then I'm also supposed to be measureing my 017 CHT sensor vs NOS 012 over on the other thread. So much fun stuff to do so little time.
bbrock
QUOTE(Superhawk996 @ Jan 22 2021, 05:56 AM) *

QUOTE(bbrock @ Jan 21 2021, 09:31 PM) *


As for repairing a blown resistor - how important do you suppose it is to use an open coil resistor. Would something like this work as a replacement?

https://www.digikey.com/en/products/detail/...A502R5J/2366322




It would definately work in the sense of functionality.

I think the reason for the open coil resistors is available package space and better cooling.

Looking at the size of the linked resistor, 2"L x 1"W and about the same 1" tall, I don't think it would fit. Could it have leads soldered to the resistor and then soldered to the OEM resistor holder and then mount the thing somewhere? Probably. I would be concerned about potential for the resistor to get hot enough to melt or deform plastic at 50W if JB welded to the housing or something like that. Drill holes for wires to exit the fan housing and mount that style resistor to the body as heat sink? screwy.gif Sure, depends on how bad you really need a low or medium speed. laugh.gif

The key thing I don't know is how much current is the fan pulling at start up (peak in-rush) and what is is steady state operating current. Once we know that, we could properly size the resistors. 50W might be overkill? confused24.gif


Yeah, I was wondering more about the general package style than that particular resistor. The one I linked was just a random selection of twenty-seven 2.5 Ohm chassis mounted resistors that popped up on Digikey that had a nice picture since I didn't know particular power and dimension specs needed offhand. There are many options. For example, here's a 5w resistor only 0.6" long. https://www.digikey.com/en/products/detail/...5WM2D5/11650430

I was surprised not to find a selection of open coil style resistors on Digikey which makes me think either I don't know the correct search term to use, or perhaps that style has been superseded to a modern design for the application. With thousands of resistor options available for almost any given resistance rating, there are surely suitable off the shelf options out there.

I picked the chassis mount to look at because they are mounted in heat sinks for heat dissipation which seems inline with the original design. You could mount those to a small aluminum plate with heat transfer paste for even more efficient heat dissipation.
Mikey914
I'd look at a standard more "modern" resistor as a replacement. Pretty sure the only reason these are made like this is it was less expensive to build their own than buy them in 1969.
DRPHIL914
QUOTE(bbrock @ Jan 22 2021, 09:42 AM) *

QUOTE(Superhawk996 @ Jan 22 2021, 05:56 AM) *

QUOTE(bbrock @ Jan 21 2021, 09:31 PM) *


As for repairing a blown resistor - how important do you suppose it is to use an open coil resistor. Would something like this work as a replacement?

https://www.digikey.com/en/products/detail/...A502R5J/2366322




It would definately work in the sense of functionality.

I think the reason for the open coil resistors is available package space and better cooling.

Looking at the size of the linked resistor, 2"L x 1"W and about the same 1" tall, I don't think it would fit. Could it have leads soldered to the resistor and then soldered to the OEM resistor holder and then mount the thing somewhere? Probably. I would be concerned about potential for the resistor to get hot enough to melt or deform plastic at 50W if JB welded to the housing or something like that. Drill holes for wires to exit the fan housing and mount that style resistor to the body as heat sink? screwy.gif Sure, depends on how bad you really need a low or medium speed. laugh.gif

The key thing I don't know is how much current is the fan pulling at start up (peak in-rush) and what is is steady state operating current. Once we know that, we could properly size the resistors. 50W might be overkill? confused24.gif


Yeah, I was wondering more about the general package style than that particular resistor. The one I linked was just a random selection of twenty-seven 2.5 Ohm chassis mounted resistors that popped up on Digikey that had a nice picture since I didn't know particular power and dimension specs needed offhand. There are many options. For example, here's a 5w resistor only 0.6" long. https://www.digikey.com/en/products/detail/...5WM2D5/11650430

I was surprised not to find a selection of open coil style resistors on Digikey which makes me think either I don't know the correct search term to use, or perhaps that style has been superseded to a modern design for the application. With thousands of resistor options available for almost any given resistance rating, there are surely suitable off the shelf options out there.

I picked the chassis mount to look at because they are mounted in heat sinks for heat dissipation which seems inline with the original design. You could mount those to a small aluminum plate with heat transfer paste for even more efficient heat dissipation.
that would be great if a replacement option were available , i think most of these failed in that area and in order to rebuild a box that works, it would be great to make a replacment that last a long time, good idea for the extra heat sink on the back too.
Superhawk996
Not trying to be a kill joy on the DigiKey resistors but I suspect that in the desire to find a nice "modern" looking resistor you've over looking the physics and the cooling requirements.

These packaged high watt resistors require a heat sink to last. Once that aluminum case gets hot and has no heat sink to pull the heat away, it will get too hot and burn open in short order. That's why I referenced the idea of wires exiting the HVAC case and having to mount it on the sheetmetal body as a heat sink.

Likewise, that style of heavy resistor if left unsupported within the blower case is going to fatigue the OEM resistor standoffs that were not designed to support that kind of resistor weight when dynamic road loads are imposed on it.

A thick gauge wire wound resistor in open air is going to be able to handle more current and heat rejection than a nice neat ceramic or aluminum heat sink package that looks aerospace cool.

I look at it as the industry having converged upon the best, most cost effective solution and it's not one of those DigiKey style resistors.

Poke around on internet and you'll quickly find the converged solutions are resident in the blower case, they are air cooled. Typically open wire coil, large ceramic, or Solid State with big honking cooling fins in the air stream. You'll notice in a couple that the bi-metallic thermal cut out switch has been replaced by a more modern component though!

Click to view attachment

https://www.finditparts.com/products/594700...ASABEgJSDfD_BwE

https://shop.advanceautoparts.com/p/bwd-hva...mp;gclsrc=aw.ds

https://www.walmart.com/ip/Blower-Motor-Res...BCABEgI7CfD_BwE
bbrock
QUOTE(Superhawk996 @ Jan 22 2021, 08:16 AM) *

Not trying to be a kill joy on the DigiKey resistors but I suspect that in the desire to find a nice "modern" looking resistor you've over looking the physics and the cooling requirements.


Wasn't trying to find a modern looking resistor. I was just trying to find any suitable replacement. I was actually searching for open coil resistors like what are in the blower and shocked not to be able to find them among the 500,000+ resistors in their catalog (or anywhere). I'm not saying they are not there, only that I couldn't find them.

I am a bit offended though. happy11.gif Even I'm not dumb enough to try to hang one of those chassis mount resistors from the OEM standoffs. I envisioned mounting to an aluminum plate, glued to the base of the resistor pack, and connected with flexible leads. Irrelevant if they are not suitable.

I'm still puzzled why open wire coil resistors are not easier to find. Even resistor wire is kind of hard to find. All the stuff I've seen is annealed and too soft to make those spring like coils.
bdstone914
QUOTE(bbrock @ Jan 22 2021, 09:03 PM) *

QUOTE(Superhawk996 @ Jan 22 2021, 08:16 AM) *

Not trying to be a kill joy on the DigiKey resistors but I suspect that in the desire to find a nice "modern" looking resistor you've over looking the physics and the cooling requirements.


Wasn't trying to find a modern looking resistor. I was just trying to find any suitable replacement. I was actually searching for open coil resistors like what are in the blower and shocked not to be able to find them among the 500,000+ resistors in their catalog (or anywhere). I'm not saying they are not there, only that I couldn't find them.

I am a bit offended though. Even I'm not dumb enough to try to hang one of those chassis mount resistors from the OEM standoffs. I envisioned mounting to an aluminum plate, glued to the base of the resistor pack, and connected with flexible leads. Irrelevant if they are not suitable.

I'm still puzzled why open wire coil resistors are not easier to find. Even resistor wire is kind of hard to find. All the stuff I've seen is annealed and too soft to make those spring like coils.



@bbrock

I can supply you a good used resistor assembly.
bbrock
QUOTE(bdstone914 @ Jan 22 2021, 11:18 PM) *

QUOTE(bbrock @ Jan 22 2021, 09:03 PM) *

QUOTE(Superhawk996 @ Jan 22 2021, 08:16 AM) *

Not trying to be a kill joy on the DigiKey resistors but I suspect that in the desire to find a nice "modern" looking resistor you've over looking the physics and the cooling requirements.


Wasn't trying to find a modern looking resistor. I was just trying to find any suitable replacement. I was actually searching for open coil resistors like what are in the blower and shocked not to be able to find them among the 500,000+ resistors in their catalog (or anywhere). I'm not saying they are not there, only that I couldn't find them.

I am a bit offended though. Even I'm not dumb enough to try to hang one of those chassis mount resistors from the OEM standoffs. I envisioned mounting to an aluminum plate, glued to the base of the resistor pack, and connected with flexible leads. Irrelevant if they are not suitable.

I'm still puzzled why open wire coil resistors are not easier to find. Even resistor wire is kind of hard to find. All the stuff I've seen is annealed and too soft to make those spring like coils.



@bbrock

I can supply you a good used resistor assembly.


Thanks Bruce, Mine's actually in excellent condition and working well. I was just curious what replacement options for resistors were. It shouldn't be as hard as it seems to be. I get a perverse pleasure out of such challenges.
Superhawk996
QUOTE(bbrock @ Jan 22 2021, 10:03 PM) *


I am a bit offended though. happy11.gif


@bbrock Here to serve! lol-2.gif I'm sure with a little time, you'd master the process to harden and then temper the annealed wire properly to roll your own!
Superhawk996
Well it turns out I will be posting a WTB.

My blower works on all three speeds but the plastic housing is pretty rough. Cracked, missing clips that hold the 1/2's together, and one set of clip mounts is broken off completely. Motor vibrates like bearings/bushings are worn and/or needs to be rebalanced.

Not sure who messed with my car somewhere in it's life but it was certainly owned at some point by the type of person that you could lock in an empty room, alone with two ball bearings. Come back 1 hour later and they would have broken one and lost the other. av-943.gif

OK, here are my measurements. Hope this helps you troubleshoot yours. @DRPHIL914

Click to view attachment

All were measured at 70F so amperage could be sustantially higher on cold morning with a sluggish motor that is drawing current closer to stall current. I'm surprised at the current this little bugger of a motor can draw! No wonder it's on a 25A fuse!

Click to view attachment
DRPHIL914
QUOTE(Superhawk996 @ Jan 24 2021, 01:35 PM) *

Well it turns out I will be posting a WTB.

My blower works on all three speeds but the plastic housing is pretty rough. Cracked, missing clips that hold the 1/2's together, and one set of clip mounts is broken off completely. Motor vibrates like bearings/bushings are worn and/or needs to be rebalanced.

Not sure who messed with my car somewhere in it's life but it was certainly owned at some point by the type of person that you could lock in an empty room, alone with two ball bearings. Come back 1 hour later and they would have broken one and lost the other. av-943.gif

OK, here are my measurements. Hope this helps you troubleshoot yours. @DRPHIL914

Click to view attachment

All were measured at 70F so amperage could be sustantially higher on cold morning with a sluggish motor that is drawing current closer to stall current. I'm surprised at the current this little bugger of a motor can draw! No wonder it's on a 25A fuse!

Click to view attachment


thanks foe the info, just pulled my original fan and housing and just sitting here checking resistance of each circuit i get less than 1 ohm on each one , in fact all 3 test at about .8.
so i guess new resistor pack is necessary, but i will be pulling this apart, the fan does not turn easily, new bearing ans seals and maybe motor , will see if i can clean it all up once it’s out , doesn’t look too good, it’s been apart before someone put it back together and used silicone sealant between the upper and lower parts ugh.
Superhawk996
@DRPHIL914

" . . . so i guess new resistor pack is necessary". Not mentioning to beat you up but to reinforce how it important RULE #1 is in electrical trouble shooting. We've all done this. It was trained out of me and then has been proven by over 30 years of troubleshooting both electrical and mechanical systems.

Sounds to me first thing to do is to pull the resistor pack. Verify -- don't assume.

Resistors usually fail open. It is very rare for a resistor to fail as a short.

If you have 0.8 ohms on all three, it sounds to me like the bimetallic switches are continiously closed. Could be similar to Brent's situation. In his case, he had one of them closed all the time and tweaked it with a pair of pliers to be normally open as it should be. Testing with DMM can verify this.

Click to view attachment

However, if this is the case, you really should have 3 high speeds already.

You can bench test the fan with 12v battery and some wire jumpers. Did you try that by chance?

Lack of airflow could have overheated the resistors and caused the bi-metallic switches to become deformed and to have become normally closed instead of normally open per the schematic. That is a theory and an assumption. A bench test of the reistor pack and of the fan itself will verify or disprove that hypothesis.

DRPHIL914
QUOTE(Superhawk996 @ Jan 25 2021, 07:42 AM) *

@DRPHIL914

" . . . so i guess new resistor pack is necessary". Not mentioning to beat you up but to reinforce how it important RULE #1 is in electrical trouble shooting. We've all done this. It was trained out of me and then has been proven by over 30 years of troubleshooting both electrical and mechanical systems.

Sounds to me first thing to do is to pull the resistor pack. Verify -- don't assume.

Resistors usually fail open. It is very rare for a resistor to fail as a short.

If you have 0.8 ohms on all three, it sounds to me like the bimetallic switches are continiously closed. Could be similar to Brent's situation. In his case, he had one of them closed all the time and tweaked it with a pair of pliers to be normally open as it should be. Testing with DMM can verify this.

However, if this is the case, you really should have 3 high speeds already.

You can bench test the fan with 12v battery and some wire jumpers. Did you try that by chance?

Lack of airflow could have overheated the resistors and caused the bi-metallic switches to become deformed and to have become normally closed. That is a theory and an assumption. A bench test will verify that hypothesis.

completely agree, but just didnt have time last night,

plan for tonight is to bench test wit the batter charger, put 12 volts in there and see what we get, then pull it out so i can inspect the resistor pack up close, see if that bi-metallic strip is stuck together. so will verify . the resistance values seemed strange to me to, was trying to figure out how it would fail that way. fan does not spin freely so so doubt i have to get this one pulled apart and cleaned up and see if lub will help. Ive heard that the motors really dont fail or burn out often, dont know if that is true,
But talked to Bruce Stone over the weekend and he suggested doing the same bench test, inspection, etc. and i have all new seals and hardware coming from Mark too.

will report back tonight.
Superhawk996
QUOTE(DRPHIL914 @ Jan 25 2021, 08:10 AM) *

. . . plan for tonight is to bench test wit the battery charger . . .


Would be better to use a 12v battery as the source if you can. Battery chargers vary widely and some are really only 1/2 wave rectified and don't have a full 12 volt steady output. It can cause the fan motor to run slower than it would with a battery.

Likewise, it may be current limited. I tested stall current with a battery and it pulled 15A or so. If the battery charger can only deliver 10A, you may not get full speed and/or have sufficient amperage to turn motor if it is binding a little.


Here is what I mean by 1/2 wave output. Can go to site if you want more info.

Click to view attachment
Superhawk996
@DRPHIL914

I'm going to pick one more snippet from your quote. Not trying to beat up on you personally, but, it speaks to Rule #2. If I'm making you mad by picking out snippets, I'll stop, just let me know. However, it illustrates how I got to the rules we started with.

" . . . the resistance values seemed strange to me to, was trying to figure out how it would fail that way."

This is why a good schematic is a must have. Depending on the complexity of the system, It can be hard, if not impossible troubleshoot effectively without a schematic.

Good schematic from Haynes. B&W is a bit more work to read for color codes but all info is available. The schematic explains the switches, their normal position, and their operation.

Click to view attachment


Nice for color codes, but, a block diagram is useless for this type of troubleshooting. Explains nothing other than the colors of the wire.

Click to view attachment
DRPHIL914
QUOTE(Superhawk996 @ Jan 25 2021, 08:38 AM) *

@DRPHIL914

I'm going to pick one more snippet from your quote. Not trying to beat up on you personally, but, it speaks to Rule #2. If I'm making you mad by picking out snippets, I'll stop, just let me know. However, it illustrates how I got to the rules we started with.

" . . . the resistance values seemed strange to me to, was trying to figure out how it would fail that way."

This is why a good schematic is a must have. Depending on the complexity of the system, It can be hard, if not impossible troubleshoot effectively without a schematic.

Good schematic from Haynes. B&W is a bit more work to read for color codes but all info is available. The schematic explains the switches, their normal position, and their operation.

Click to view attachment


Nice for color codes, but, a block diagram is useless for this type of troubleshooting. Explains nothing other than the colors of the wire.

Click to view attachment


no, please i appreciate the info, and being educated!
help me understand the basics like being able to read the schematics will help me trouble shoot other issues in the future,

so the M is the motor correct, and #3 high does not go thru either of the resistors, just the bimetalic plate? if the plate were not conducting current you would not get the fan to run on that setting and resistance with be infinity(short?)
Superhawk996
@DRPHIL914

so the M is the motor correct -- Yes, Correct

and #3 high does not go thru either of the resistors -- Correct

. . if the plate were not conducting current you would not get the fan to run on that setting -- can't really answer that question without a physical inspection of the assembly. I tried to look at BeatNavy's photos and I still can't tell for sure. However, I can see from the photo the plate is basically a thick, solid copper trace. The chance of that opening up is slim to none. The amount of current it would take to melt that open would have melted the external wiring 1st. I think I might be misunderstanding the question. Let's call the switches; bi-metallics switches. What I'm calling the plate is the structure that the reistors and the bi-metallic switches are attached to. So when a bi-metallic switch is normally open you would read the resistance of the Motor + the resistor. When the bi-metallic switch is closed (should only be when the resistor is over heating), the bi-metallic switch deforms to the closed position, and bypasses the resistor with a short (zero ohm) connection, and the motor would run in high speed (just like position #3), the fan should pull more air across the resistor, cool it down, and then the bi-metallic switch should return to the normally open position and the fan would return to its regulated speed. If the bi-metallic switch were permanently deformed to be normaly closed (even when cool) then you would read the motor resistance only just like you would in position #3.

and resistance with be infinity(short?) -- A short = 0 ohms, open circuit = infinity. Since you are reading 0.8 ohm on all three speeds, we know the plate is not open and, that we have conductivity between all three potential current paths though the motor


Adding on: Around each resistor, you see a switch that operates as a square wave. Either OFF or ON. When that switch closes, you have a short around the wire wound resistor. Therefore, you would only read the motor winding resistance when measuring though the switch if this switch were closed. These are the bi-metallic switches that are located blow the resitors in Brent's photo.

Note: DMM's can have 0.1- 0.3 ohm of resistance just in the leads (especially if using add-on's like alligator clips. My cheap DMM reads 0.2 ohms with a dead short and alligator clips attached. So moral of the story is your ohm readings may differ slightly and/or a dead short may still show as 0.2 ohms or so.
DRPHIL914
took the sucker apart and retested the resistor pack without being hooked up to motor,

values are:
Low- 1.5
Medium- 3.4
high- 1-1.5

@Superhawk996

pictures of it show both bimetallic strips in good condition and open
bbrock
QUOTE(DRPHIL914 @ Jan 25 2021, 05:14 PM) *

took the sucker apart and retested the resistor pack without being hooked up to motor,

values are:
Low- 1.5
Medium- 3.4
high- 1-1.5

@Superhawk996

pictures of it show both bimetallic strips in good condition and open


Where are placing the probes to measure resistance and do you see any resistance specs on the resistor pack? My is stamped 2.5 ohms for the low speed resistor and 0.75 for medium speed. Measuring resistance with probes on each end of the resistor, I got 2.5 ohms on the nose for the low side, and 1.1 ohms on the medium side. The medium sides was higher than what was stamped but works okay so I think those stamps are ballpark.
Superhawk996
@DRPHIL914

Agree with @bbrock 's comments, need to know exactly where you measured from both initially and on this latest round of measurements.

Before we go there, let's acknowlege something changed that doesn't make sense. If you were measuring 0.8 ohms on all three settings before and now you're measuring higher resistances with the resistor pack disconnected from the motor, something is wrong.

The motor + a resistance value should always be higher than just measuring the resistors alone. Since resistances went up since 1st round, something isn't correct.

Another key item that is basic to electronics work is that in order to measure resistance, the component (or system) under measurement must be disconnected from the rest of the system. For example, we cannot measure the resistance of the fresh air motor + resistor with the motor assembly plugged into the rest of the vehicle wiring and HVAC slider controls. I assumed the fresh air box was completely disconnected from the vehicle when the 0.8 ohms was reported but maybe I made a bad assumption despite my own Rule #1. laugh.gif See, we all do it despite our best attempt.

This is probably a good point to talk about Rule #4, half splitting. The goal is to divide things in 1/2 to isolate which side the problem is on. By disconnecting the fan motor & resistor assembly, we dive the system into two. The vehicle side (vehicle wiring, HVAC control, connectors) and the fresh air box assembly (motor, resistor, and the short bit of wire inside).

I had assumed we were working on just the 1/2 system of the fresh air box completely disconnected from the vehicle and wiring. Is that valid?

To continue the 1/2 split conversation, we can now split the fresh air box system in 1/2 again. We can divide system to the motor only disconnected from the resistor pack, and the resistor+stub of wire that connects to the motor.

So on the resitor pack; disconnected from the motor, (1/4 of the sytem as we currently have it divided) I'd like you to measure the resistors only (measure one resistor post to the other resistor post) with nothing else connected to it. That will give us the value of the two resistors alone.

By inspection we can see the bi-metallic switches are open. We might measure that later just to be sure but for now let's just get the resistor values and see if they come close to Brent's or BeatNavy's measurements and/or markings on the housing.

The other thing we can do is to measure the other 1/4 of the system (the motor only). With the resistor pack disconnected from the motor, what does the motor resistance measure? Does it change drasticallywhen you rotate the position of the fan impeller from one position to another?

We can also physically test just the fan -- it can be hooked to a 12 volt battery to see if it spins.

Let's try this and see where we end up as we try to resolve why the system changed. Worst case, we will put the motor + resistor 1/2 of the system back together and can see if we can duplicate your original 0.8 ohm measurements. Not likely to have to do this once we go through the steps above.
DRPHIL914
QUOTE(Superhawk996 @ Jan 26 2021, 07:11 AM) *

@DRPHIL914

Agree with @bbrock 's comments, need to know exactly where you measured from both initially and on this latest round of measurements.

Before we go there, let's acknowlege something changed that doesn't make sense. If you were measuring 0.8 ohms on all three settings before and now you're measuring higher resistances with the resistor pack disconnected from the motor, something is wrong.

The motor + a resistance value should always be higher than just measuring the resistors alone. Since resistances went up since 1st round, something isn't correct.

Another key item that is basic to electronics work is that in order to measure resistance, the component (or system) under measurement must be disconnected from the rest of the system. For example, we cannot measure the resistance of the fresh air motor + resistor with the motor assembly plugged into the rest of the vehicle wiring and HVAC slider controls. I assumed the fresh air box was completely disconnected from the vehicle when the 0.8 ohms was reported but maybe I made a bad assumption despite my own Rule #1. laugh.gif See, we all do it despite our best attempt.

This is probably a good point to talk about Rule #4, half splitting. The goal is to divide things in 1/2 to isolate which side the problem is on. By disconnecting the fan motor & resistor assembly, we dive the system into two. The vehicle side (vehicle wiring, HVAC control, connectors) and the fresh air box assembly (motor, resistor, and the short bit of wire inside).

I had assumed we were working on just the 1/2 system of the fresh air box completely disconnected from the vehicle and wiring. Is that valid?

To continue the 1/2 split conversation, we can now split the fresh air box system in 1/2 again. We can divide system to the motor only disconnected from the resistor pack, and the resistor+stub of wire that connects to the motor.

So on the resitor pack; disconnected from the motor, (1/4 of the sytem as we currently have it divided) I'd like you to measure the resistors only (measure one resistor post to the other resistor post) with nothing else connected to it. That will give us the value of the two resistors alone.

By inspection we can see the bi-metallic switches are open. We might measure that later just to be sure but for now let's just get the resistor values and see if they come close to Brent's or BeatNavy's measurements and/or markings on the housing.

The other thing we can do is to measure the other 1/4 of the system (the motor only). With the resistor pack disconnected from the motor, what does the motor resistance measure? Does it change drasticallywhen you rotate the position of the fan impeller from one position to another?

We can also physically test just the fan -- it can be hooked to a 12 volt battery to see if it spins.

Let's try this and see where we end up as we try to resolve why the system changed. Worst case, we will put the motor + resistor 1/2 of the system back together and can see if we can duplicate your original 0.8 ohm measurements. Not likely to have to do this once we go through the steps above.



i can do more of this tonight. to answer a few questions, when i tested it and got the.8, we had the 1/2 split, i was testing the fan assembly out of the car, but motor in
and i dont know what was wrong with reading but fan was hooked up , my new readings were with the fan split so just testing the resistors from neutral to each lead with aligator clips and did it with the probe on end or side of the male connector and reuslt was exactly the same, the 1.5, 3.5 and 1.0 for high which seems strange .

i will try and test the fan motor tonight and give it power, see how it turns,

Phil
now we can test the sliders by its self, i tried but was not doing something correctly as i didnt get a proper value.
Superhawk996
QUOTE(DRPHIL914 @ Jan 26 2021, 11:27 AM) *


. . . I will try and test the fan motor tonight and give it power, see how it turns,

Phil
now we can test the sliders by its self, i tried but was not doing something correctly as i didnt get a proper value.



@DRPHIL914
Before we go to the sliders we still need to figure out whats going on in this 1/2 of the system. Let's not assume that if resistors are OK that the problem isn't on this 1/2. Test & verify in a methodical manner before we rule anything out.

Plan:

1) Let's verify resistors:
a. Test each reistor from from post to post and report those values - should be close to the other guys. Note: be sure your test leads are scratching the surface of the posts a bit to get down to clean copper. Oxidation on copper traces will add some resistance.
b. You'll notice that two of the reisistors are tied together. This is the end of the resistor bank that should lead to the motor and should also be connected to the high speed pin per the schematic.

2) Bench test just the motor

3) Let's assume the resistors measure OK. I'd like to put the motor / resistor back together and re-verify resistances. We need to understand why your low and high resistances were the same. I suspect we have the ground reference point wrong either per your measurement technique or how I labeled the connector. I'll try to re-verify my connector and reverify my measurements on my blower to make sure I drew that right.

4) Bench test the motor + resistor assembly. Verify all three speeds work on the bench.

Let's do that before we move to other potential causes in wiring and/or in control levers.
DRPHIL914
@Superhawk996

i went back and retested the resistors like you suggested, post to post same results, then i hooked up the motor to the leads, rechecked the low and medium we’re about same , the high on the other hand was like 121?? here are pictures-
the high post is the one with red wire(+) that goes to motor, from motor that brown ground wire (-) goes back to the resistor pack so the black lead is on that post for each test.
i did not bench test the motor with 12v but i can tell you it’s difficult to turn by hand it’s not freely spinning, housing is apart and the fan seal broke and no one makes them yet- hey Mark! @Mikey914 poke.gif
also pictures of the fan motor assembly, it’s now out. it’s different than the new ones, they don’t have the metal housing like this. anyone order one of the new ones from URO or Porsche?

how do you take the motor out of the white fan part? i took the black top part off by taking the 3 spring clips off that hold those 2 parts together - the black part holds the big seal .
Superhawk996
@DRPHIL914

Great job gutting that beast! Especially so if you did it without breaking any of the clip plastic stanchions.

We've got a mystery. Love it.

So the good news is that youre saying the resistors roughtly make sense measued post to post.

Low = 1.5 ohm initial to 2.1 ohm 2nd time. Perfect!
Medium = 3.4 ohm initial to 4.0 ohm 2nd time Perfect!

High = something is jacked up.

I'm a little leary of your meter given that very 1st round of measurements measured 0.8 ohm on everything and now things are measuring much better for the medium and low resistors but way, way off for High. Something very odd going on here. We're going to stay here for a bit until we can 1) verify your meter is OK, or 2) Get repeatability to the readings, or 3) find some other root cause that explains all this weirdness.

Ideas to move forward:
1) Are you abslolutely sure the meter leads aren't having connectivity issues of their own? I've had leads similar to yours, where you can unsrew the plastic lead housing from the metal tip, and the lead wire is soldered to the test tip. I've had bad solder joints on these type of leads before. Beware of these type test leads.

Click to view attachment

a) I'm going to assume this isn't likely and that you performed the low and medium measurements after doing high and getting 121 ohm on high and by measuring 4 ohm type connections on M & L immediatly following the 121 ohm we can be partially convinced the problem isn't in the test lead.

2) When you did measure the high postion is there any chance the aligator clip wasn't making good connection on the high post? If you tried wiggling the aligatior clips to scratch the post and/or pressed the clip together while wiggling to get though any post corrostion and you measured 121 ohms multiple times, we'll assume it wasn't a fluke of the connection of the test lead.

3) If High is indeed repeatable at 121 ohms:
a) let's look very closely at the copper trace connections on the resistor block for small crack, signs, of corrosion, or bad connectivity.

b) Are the connector pin posts soldered? I think I recall they are. Could be a cold solder joint between the high post and the wire and/or copper trace. Sometimes you can see a cold solder joint with a 5-10x loupe. Other times I've just had to re-heat the solder and it improves.

c) any chance the motor rotated ever so slightly between measuring L & M to when you measured High? I'm wondering if the motor brushes are worn and all of sudden had high resistance to the motor commutator when you happened to measure high?

I'll tear my blower down tonight and to verify how the resistor pack is built and see if I can get some good photos to point you toward the motor brushes and the bearings to see if we can get your motor freed up in order to bench test it.
DRPHIL914
QUOTE(Superhawk996 @ Jan 27 2021, 01:37 PM) *

@DRPHIL914

Great job gutting that beast! Especially so if you did it without breaking any of the clip plastic stanchions.

We've got a mystery. Love it.

So the good news is that youre saying the resistors roughtly make sense measued post to post.

Low = 1.5 ohm initial to 2.1 ohm 2nd time. Perfect!
Medium = 3.4 ohm initial to 4.0 ohm 2nd time Perfect!

High = something is jacked up.

I'm a little leary of your meter given that very 1st round of measurements measured 0.8 ohm on everything and now things are measuring much better for the medium and low resistors but way, way off for High. Something very odd going on here. We're going to stay here for a bit until we can 1) verify your meter is OK, or 2) Get repeatability to the readings, or 3) find some other root cause that explains all this weirdness.

Ideas to move forward:
1) Are you abslolutely sure the meter leads aren't having connectivity issues of their own? I've had leads similar to yours, where you can unsrew the plastic lead housing from the metal tip, and the lead wire is soldered to the test tip. I've had bad solder joints on these type of leads before. Beware of these type test leads.

Click to view attachment

a) I'm going to assume this isn't likely and that you performed the low and medium measurements after doing high and getting 121 ohm on high and by measuring 4 ohm type connections on M & L immediatly following the 121 ohm we can be partially convinced the problem isn't in the test lead.

2) When you did measure the high postion is there any chance the aligator clip wasn't making good connection on the high post? If you tried wiggling the aligatior clips to scratch the post and/or pressed the clip together while wiggling to get though any post corrostion and you measured 121 ohms multiple times, we'll assume it wasn't a fluke of the connection of the test lead.

3) If High is indeed repeatable at 121 ohms:
a) let's look very closely at the copper trace connections on the resistor block for small crack, signs, of corrosion, or bad connectivity.

b) Are the connector pin posts soldered? I think I recall they are. Could be a cold solder joint between the high post and the wire and/or copper trace. Sometimes you can see a cold solder joint with a 5-10x loupe. Other times I've just had to re-heat the solder and it improves.

c) any chance the motor rotated ever so slightly between measuring L & M to when you measured High? I'm wondering if the motor brushes are worn and all of sudden had high resistance to the commutator when you happened to measure high?

I'll tear my blower down tonight and to verify how the resistor pack is built and see if I can get some good photos to point you toward the motor brushes and the bearings to see if we can get your motor freed up in order to bench test it.



i did rotate the motor while hooked up and on the low and medium they change of course during turning it and return to the static number, the high same way, it returns to the 120 reading like 3x , on off back, test side and end of then. yes they are soldered , will try and clean contacts a bit and recheck the positive/high lead, have to find my solder gun, but they look and feel solid.
DRPHIL914
i am going to get new leads, yes mine pulled apart like that and i re- attached it , soldered it back but the other one not so good, so next step get that motor freed up, try and source a new seal/replacement, bench test the motor,
but i do have a fan motor assembly coming from Al Merideth he had a good one, so if this doesnt get fixed i had a spare on hand soon, but goal here is to get this tested figured out and fixed and rebuilt and working, so onward ho!!!!
914werke
QUOTE(DRPHIL914 @ Jan 27 2021, 09:29 AM) *
anyone order one of the new ones from URO or Porsche?

Ive sold a couple of them HERE never had any feedback (pro or con) from those sales confused24.gif
Superhawk996
@Mikey914

I'll put in a 2nd vote for wish list of this gasket between motor and the blower housing. I can see mine is dry rotted too. Would be lovely to have a complete foam package available, blower motor to blower housing, blower vane seals, blower to upper housing, upper housing to body.

When I tear mine down to resolve the motor vibration and to clean I'm sure I'll destroy the foam too. Obviously cheapo Home Depot suff could be used in a pinch but it would be sweet to get a whole kit as one stop shopping.

I've got a second unit on it's way to me because my upper housing is cracked and has cracked drain tube so I'm assuming that unit will likely need new foam too.
bbrock
Hey Phil, if those pics show where you are measuring the resistance, I still don't think you are getting an accurate read on just the resistors. You should clip the probes to the ends of the resistors themselves rather than the connector pins. I'd have to look at the schematic again but I think it might still be measuring through the motor since it is still connected to the harness.
Mikey914
Actually I've been working on a more complete kit for this type of We have made the seal you speak of. That and a bunch more parts.
@drphil914 has a care package I sent him you will see shortly. I will be opening up a GB as soon as he completes the build.
Mark
Superhawk996
QUOTE(DRPHIL914 @ Jan 27 2021, 12:29 PM) *


how do you take the motor out of the white fan part?


@DRPHIL914

After having just totally screwed up my blower motor trying to remove the impeller all I can say is DON'T DO IT. lol-2.gif

I was willing to risk mine since the fan was vibrating so badly and I could feel significant side play in the shaft. Likewise the impeller already had several cracked vanes before I started this that were deflecting and also causing vibration. I had little to loose.


What a fiasco. It's pretty rare that I get into disassembling something and then realizing that I've just Fuched it up beyond all hope. But this motor assembly is it.


The bottom line is the impeller is held on by a spring clip that clamps the impeller to the shaft. Mine would not release even after removing the clip. Gentle persuasion didn't work. A bit of gentle warming to sofen the platic relative to the steel shat. Nope. Then came the hammer smash.gif for a gentle tap and then all hell broke loose.

I'm not sure I even want to go into the rest of the story. Needless to say, this one ain't ever gonna be the same again. RIP. headbang.gif

On this next unit I have coming I'll hope it is starting from a better place than this one was which was clearly heavily molested before I got to it. If the impeller is filthy and broken like mine was on this one, I'd just clean carefully with alcohol and then just carefully super glue the cracked vanes and that is all.

I also noticed that the impeller was balanced as a motor/impeller assembly so by removing the impeller, it would likely only have compounded my vibration problems even discounting for the motor shaft side play. I marked mine in anticipation of this but the reality is that it was going to be a gamble if I could even assemble it with the fan clocked correctly had all the other bad stromberg.gif not happened.
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