Defrost fan rehab and rebuild thread (fresh air fan), or How the heck do if fix this thing? Options

[Superhawk996]

. . . 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 (IMG:style_emoticons/default/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.



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]

@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.



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]

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 (IMG:style_emoticons/default/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]

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. (IMG:style_emoticons/default/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 (IMG:style_emoticons/default/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. (IMG:style_emoticons/default/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 (IMG:style_emoticons/default/stromberg.gif) not happened.

[DRPHIL914]

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. (IMG:style_emoticons/default/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 (IMG:style_emoticons/default/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. (IMG:style_emoticons/default/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 (IMG:style_emoticons/default/stromberg.gif) not happened.

@Superhawk996

lol!!! (IMG:style_emoticons/default/w00t.gif) sorry to hear about the impeller fiasco! i am not sure how you would take the motor out without breaking the fan.
i just got the new blower from Al and the fan is free and clear and spins smoothly.
just tested the static resistance and i get, 2.6 & 4.4 but on the high circuit 2.5 with motor hooked up. without motor in the circuit, it’s 2.8 low, 4.2 medium and 1.7 high,- looks like low and medium should be switched, i am sure i have the contacts located correctly.- also tested between each circuit, so those were
5.2 between low-medium posts( the 2 resistors combined?) 4.6 low-high, 2.8 medium-high, . do those number look better than the other fan?

[DRPHIL914]

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

@Mikey914
@Superhawk996
man that seal looks good, that’s awesome you had made these you know they are not made by anyone else!!!
i am still going to try and figure out why the values on my fan are not correct and high circuit does not conduct, or complete a circuit but i got a good used one from Al Merideth, and it spins free, fins are perfect, and the test on the circuits is promising, so that will be the one we rebuild and put new seals in with the new kit coming.

Phil

[Superhawk996]

@DRPHIL914

Sure looks a lot better than 121 ohms on high and/or 0.8 ohms on all three which are were two of the sort of random conditions that you had on the other motor assembly.

I'm wondering if you have some sort of resolution issue on you meter down at very low ohm setting. I have have serveral DMM's and a couple older analog multi-meters for special purposes. I have a cheap Sunpro DMM/Tach/Dwell meter that doesn't do well at low (sub 10 ohm) type work. Works great for Tach and dwell but I never trust it for resistance measurements.

Out of curiosity, when you touch the test leads together do you get something very close to zero ohms . . . like maybe 0.1 or 0.2 ohms? Is it repeatable?

The other thing that may be going on keeping high from showing lower resistance is the commutator may not be clean. I'd be curious if the resistance goes down after you run it on the bench for a few mintues and the brushes wipe across the commutator for a while.

FYI -- in the process of destroying my fan motor, it was clear that the brushes in mine are non-serviceable. The only real reason after that for wanting to remove the impeller was to try to get some lubrication on the rear bushing that is largely obscured by the impeller. I'll find a better way on the new unit coming.

I may order one of the fan motors from Pelican just so we can document how well those work and fit. Might be nice to have a brand spanking new motor. Probably will wait to see what shape this second fresh air box and blower is in that I just purchased as WTB before I pull the trigger on that idea.

Interesting that the end of your motor appear to be capped over the bushings. Mine weren't. Either the design had changed or someone had previously pulled them off my motor long ago when the housing was 1st opened, clips broken, and it was molested.

[Superhawk996]

I'll snap some photos of my resistor pack tonight and we'll label each of the traces and reverify all pin connections.

[Superhawk996]

Warning: Carnage that can ensue trying to disassemble the blower motor

First up someone was clearly here before and made some creative rubber seals for the blower motor control vanes.





Looking forward to purchasing 914Rubber foam seals.

Should you decide to remove the impeller the 1st step is to get the spring clip off. I did it by gently prying the clip upward until I could get ahold of it with expanding snap ring pliers.



In the cascading events that lead me to remove the motor from the housing / frame, it lead to a complete FUBAR situation. The permanent magnets and a bunch of spring clips that hold the magnets inside the housing came out along with the motor frame. I had assumed the permanent magnets would be secured to the housing. They were. However the glue that was holding them was so old, they just slipped right out of the frame along with the rest of the armature frame assembly. I don't see this ever going together properly again! Given the result, I would not recommend trying to remove the motor from the housing unless you're planning to replace the complete motor assembly.

Brushes weren't designed to be serviced, though it could be done if need be by unsoldering them, and carefully bending the retainers to get the brushes out. But, truly not designed for service. (IMG:style_emoticons/default/blink.gif)

The other is the motor shaft bushings are not designed for service. If they are worn and allowing side play and vibration like mine was, I don't really seee a viable way to service them even with the entire motor frame readily in my hand. (IMG:style_emoticons/default/sad.gif)

[Mikey914]

Can you post up some close up pics of the unserviceable part. Perhaps we can make a part that allows replacement of the one side that is an issue?

[DRPHIL914]

Warning: Carnage that can ensue trying to disassemble the blower motor

First up someone was clearly here before and made some creative rubber seals for the blower motor control vanes.





Looking forward to purchasing 914Rubber foam seals.

Should you decide to remove the impeller the 1st step is to get the spring clip off. I did it by gently prying the clip upward until I could get ahold of it with expanding snap ring pliers.



In the cascading events that lead me to remove the motor from the housing / frame, it lead to a complete FUBAR situation. The permanent magnets and a bunch of spring clips that hold the magnets inside the housing came out along with the motor frame. I had assumed the permanent magnets would be secured to the housing. They were. However the glue that was holding them was so old, they just slipped right out of the frame along with the rest of the armature frame assembly. I don't see this ever going together properly again! Given the result, I would not recommend trying to remove the motor from the housing unless you're planning to replace the complete motor assembly.

Brushes weren't designed to be serviced, though it could be done if need be by unsoldering them, and carefully bending the retainers to get the brushes out. But, truly not designed for service. (IMG:style_emoticons/default/blink.gif)

The other is the motor shaft bushings are not designed for service. If they are worn and allowing side play and vibration like mine was, I don't really seee a viable way to service them even with the entire motor frame readily in my hand. (IMG:style_emoticons/default/sad.gif)

i was afraid of something like that happening when and if i got that circular spring clip off the back, i think it may be better to get a new assembly with motor and install that. the URO one i have seen as cheap as $83, on ebay and other sellers Pelican was the most at $95,
very creative on the flapper seals, the other box i rebuilt 2 years ago with the main body seal and flapper seals from 914rubber were a tight but proper fit and will make that work fine. I still have to pull that one out of my car because i have to go thru this whole process of testing the contacts like we are doing on these 2, thats the one that only runs on one speed, medium. I plan on rebuilding all 3 of these unless this resistor pack is bad on #1, if so i will have to buy a good used one from someone that may have one that the rest of the housing is not worth rebuilding or isnot going to.
I do get about .5-1 testing lead to lead, so it may be the numbers i reported are slightly hig

[Superhawk996]

Note: Really need to remove resistor pack to do this properly.

When I removed mine, I found the low speed resistor bi-metallic switch was deformed closed. However, due to corrosion on the switch it was actually reading as if the switch were open. (IMG:style_emoticons/default/lol-2.gif) Can't assume anything.



So reminder on the contact positions and keyway positions.



Let's roll though the verification of the resistor

Here is the low speed after I filed the bi-metallic switch contact lightly with an ignition file. Because the bi-metallic switch is closed and now making contact it's measuring as a 1.1 ohm short across the resistor - bascially acting like a high speed bypass.



Note: from here on out I have the resistor bank leads that would normally go to the motor shorted together in same manner as @DRPHIL914 was doing previously

Now low speed again with the bi-metallic switch bent back to open position with a pair of pliers to put it where it should be.



Medium speed with bi-metallic switch open



High speed (no resitor, and no bi-metallic switch for this one basically a direct short).



Finally here is a picture of the orientation of the resistor bank connector and keyway as I photographed it in the photos above.



I also did measure the armature of my now defunct motor -- the armature of the motor measured in the range of 0.8 ohms to 1.2 ohms depending on where it was rotated to.

So if you're measuring the resistor bank in the as installed postion, you would expect all values above to have 0.8 - 1.2 ohm added to them. This correlates pretty well to what I measured initially on my blower motor + resistor as an assembly.

[Superhawk996]

@Mikey914

Here is the motor frame.



The motor brush is circled in red. In order to service it the tab would have to be bent open, the brush desoldered from the inductor / solder tab and then a new one installed. Not impossible but it's definately not designed for service.

The arrow pointing to the bushing on the open end of the motor does appear to have a small spot that can be oiled on some exposed felt. The impeller end of the motor frame doesn't have this same opening. Sort of makes sense since the impeller effectively prevents you from servicing that end of the motor.

On my blower motor I have excesive radial play in the impeller end bushing which would logically wear 1st since the impeller is cantilevered off this end. That radial play allowed it to vibrate and squeal intermittently until it warmed up.

The bushing is esentially staked into the pot metal motor frame. Wouldn't be easy to unstake it and then replace the bushing and re-stake. I'm a cheap SOB but really that would have been more work than I'd want to do. At that point, I really needed a new motor.



Hope all this can help someone someday!

[Mikey914]

Bosch has motors listed for these. If you have removed the unit this far you can save a few $ and get the Bosch brand. I have seen them for al little as $65 at one point.