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

[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.

[Superhawk996]

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.

@Mikey914

Would be curious to see what you're thinking of. Do you have a part number?

I'll do a little digging too. I'm only aware of the URO part. However, I think it really does look like what maybe a off the shelf motor with some sort of molded adapter to fit this 914 blower housing frame that this smaller motor frame was a part of.

[DRPHIL914]

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.

@Mikey914

Would be curious to see what you're thinking of. Do you have a part number?

I'll do a little digging too. I'm only aware of the URO part. However, I think it really does look like what maybe a off the shelf motor with some sort of molded adapter to fit this 914 blower housing frame that this smaller motor frame was a part of.

@Superhawk996
good work! the Bosch motor i have found on ebay, multiple sellers, about $75-85, and Bosch does the fan/motor assembly for about $250, so a few options depending on your time and $$ available.
i am going to get a URO assembly for one of these, i have one good motor/fan/resistor from Al , that one will get reassembled once cleaned and new seals all come from Mark and we will document the whole rebuild and assemble, retest and reinstall.
that will wait for a week as i will be gone this weekend and parts are not in yet.

[Mikey914]

The only thing you could have a problem with the URO part is the balancing "weights" I haven't seen any on their unit. Also the fins may not be identical to hold them on so if it's less and you can reuse your weights because you have disassembled far enough I would personally use the OEM.

[Superhawk996]

For what it's worth good luck balancing one of these fan impellers.

They are dynamically balanced using a tachometer and an accelerometer.

You'll notice the impeller has degree markings on it. The tachometer keeps track of RPM as the impeller/motor assembly is spun. The accelerometer is used to find at what angle the peak acceleration occurs.

Knowing that information, a weight can be installed 180 degrees off of the peak acceleration. Rinse lather repeat until vibration is minimized.

Not easy to duplicate in our hobby garages. Static balance would achieve very little.

It can be done in a trial and error way in the same way you might balance a home ceiling fan with a penny. The problem with this is 1) they spin way faster which means a very small weight has quite a large effect. 2) They have so many vanes on the impeller you have a lot more trial and error options on where to place the weight. 3) Determination of minimal vibration becomes highly subjective.

My bet is that is why the OEM motor/impeller assembly costs the money it does vs. the URO assuming it isn't balanced.

[DRPHIL914]

For what it's worth good luck balancing one of these fan impellers.

They are dynamically balanced using a tachometer and an accelerometer.

You'll notice the impeller has degree markings on it. The tachometer keeps track of RPM as the impeller/motor assembly is spun. The accelerometer is used to find at what angle the peak acceleration occurs.

Knowing that information, a weight can be installed 180 degrees off of the peak acceleration. Rinse lather repeat until vibration is minimized.

Not easy to duplicate in our hobby garages. Static balance would achieve very little.

It can be done in a trial and error way in the same way you might balance a home ceiling fan with a penny. The problem with this is 1) they spin way faster which means a very small weight has quite a large effect. 2) They have so many vanes on the impeller you have a lot more trial and error options on where to place the weight. 3) Determination of minimal vibration becomes highly subjective.

My bet is that is why the OEM motor/impeller assembly costs the money it does vs. the URO assuming it isn't balanced.

makes sense , every one i have opened up has different amounts and local of metal clips on fins that i assume are the balancing weights .
good point on the balancing, maybe Drew aka @uropartsguy will chime in and tell us if any balance testing is done

[UROpartsman]

The fan cage used in high quality URO Parts Blower Motor assembly 911 571 320 32 is indeed dynamically tested at the factory. Just pulled two random units off the shelf in the warehouse; one has a balancing clip and the other doesn't (probably didn't need it). Our impeller doesn't have degree marks, but it does have an arrow mark that's aligned with a small hole that's probably a reference point for an optical eye in the balancing device, and a screen tells the operator where to place the clip on the cage relative to the arrow.

We sell a ton of these annually (also fits 911 up to 1989) and don't get any complaints.

[Superhawk996]

The fan cage used in URO Parts Blower Motor assembly 911 571 320 32 is indeed dynamically tested at the factory.

@UROpartsman

(IMG:style_emoticons/default/smilie_pokal.gif) That is awesome. Thank you for chiming in and confirming that my asssumption was erroneous.

This blower motor assembly is looking like an even better, more viable option knowing the fan is balanced.

Out of curiosity, I'm looking for weight savings anywhere I can find them. Your blower motor housing looks to be injection molded plastic vs. the orignal cast pot metal frame.

I suspect the new DC motors are also lighter than stock.

Would you be so kind as to weight a unit? I just received a 2nd blower/housing to replace my housing that was all busted up. I'll weigh this stock one.

I would be be game to migrate to a new URO unit even if it only saves some weight of about 1/2 lb or so.

[DRPHIL914]

@UROpartsman
@superhawk996

Drew thanks for the information, i have a good stock one but we have been working on figuring out the resistor packs. I am going be ordering one of these soon for one of the fan housings that i am rebuilding. I see a lot of them on ebay i assume the are all the same? look the same , some sellers like partscontainer carry them and price varies slightly but not much. We will document the build and testing of the unit here as well if thats ok? as soon as i can get one in i will put it in unit #2 . fyi 914 rubber now makes that main seal that goes in the fan so a nice complete restoration can now be accoplished as long as that darn resistor pack is good!

Phil

[UROpartsman]

Would you be so kind as to weight a unit? I just received a 2nd blower/housing to replace my housing that was all busted up. I'll weigh this stock one.

I would be be game to migrate to a new URO unit even if it only saves some weight of about 1/2 lb or so.

No problem, the one in our photo weighs 556g / 1.226 lbs. How much does the OE weigh?

I see a lot of them on ebay i assume the are all the same? look the same, some sellers like partscontainer carry them and price varies slightly but not much. We will document the build and testing of the unit here as well if thats ok?

All of the URO brand units should be the same, don't believe we've made any running changes to these. These come in a plain brown box with a white and blue URO sticker, and a URO logo laser-marked as shown in the above photo. Documenting the build and testing would be fantastic, looking forward to it!

[Superhawk996]

No problem, the one in our photo weighs 556g / 1.226 lbs. How much does the OE weigh?

(IMG:style_emoticons/default/lol-2.gif) 2.63 lbs

Just the pot metal motor frame alone (no motor at all, no impeller, etc.) weighs in at at a portly 1.46 lbs.

I can see a URO unit in the future! (IMG:style_emoticons/default/happy11.gif)

Never realized that there were variations in the motor's and frames, but now looking back at Doc's photos, I see his motor and frame is different than what I had. (IMG:style_emoticons/default/confused24.gif) Guess VW may have had multiple sources for supply chain reasons or maybe just migrated to more efficient materials later on.

@Drphil914
@UROpartsman

[DRPHIL914]

No problem, the one in our photo weighs 556g / 1.226 lbs. How much does the OE weigh?

(IMG:style_emoticons/default/lol-2.gif) 2.63 lbs

Just the pot metal motor frame alone (no motor at all, no impeller, etc.) weighs in at at a portly 1.46 lbs.

I can see a URO unit in the future! (IMG:style_emoticons/default/happy11.gif)

Never realized that there were variations in the motor's and frames, but now looking back at Doc's photos, I see his motor and frame is different than what I had. (IMG:style_emoticons/default/confused24.gif) Guess VW may have had multiple sources for supply chain reasons or maybe just migrated to more efficient materials later on.

@Drphil914
@UROpartsman

@Superhawk996
check it out- ebay listing of a fan motor like mine that has the metal surround not plastic,
i might get one- there are 4. Bosch motor.

https://www.ebay.com/itm/Front-Blower-Motor...4.m46890.l49292

[Superhawk996]

This is what I was calling the blower housing frame, not so much the motor housing itself.



This is the heavy part!

The other motor frame is also cast pot metal and is an open metal frame. The permanent magnets were glued into the blower housing frame. Completely different DC motor construction than the motor you linked, and/or which appears to be in both your pictures and was part of the 2nd used fresh air box I recived.

Blower housing frame on left, DC motor with open frame in center, pile of permanent magnets, spring clips, and fasteners on the right.



The newer type DC motor that are in the URO blower and that you linked to are way lighter than these parts.

Hard for me to put a vintage on these parts. My car is an early 73' but has backdated bumpers, early doors, and generally a mish mash of parts from who knows where. I suspect this is an early model based on motor construction, the inlet cowl seal, and the fact that it didn't have a plastic inlet grille but some homemade window screen!

@DrPhil914

[DRPHIL914]

The fan cage used in URO Parts Blower Motor assembly 911 571 320 32 is indeed dynamically tested at the factory. Just pulled two random units off the shelf in the warehouse; one has a balancing clip and the other doesn't (probably didn't need it). Our impeller doesn't have degree marks, but it does have an arrow mark that's aligned with a small hole that's probably a reference point for an optical eye in the balancing device, and a screen tells the operator where to place the clip on the cage relative to the arrow.

We sell a ton of these annually (also fits 911 up to 1989) and don't get any complaints.

Would you be so kind as to weight a unit? I just received a 2nd blower/housing to replace my housing that was all busted up. I'll weigh this stock one.

I would be be game to migrate to a new URO unit even if it only saves some weight of about 1/2 lb or so.

No problem, the one in our photo weighs 556g / 1.226 lbs. How much does the OE weigh?

I see a lot of them on ebay i assume the are all the same? look the same, some sellers like partscontainer carry them and price varies slightly but not much. We will document the build and testing of the unit here as well if thats ok?

All of the URO brand units should be the same, don't believe we've made any running changes to these. These come in a plain brown box with a white and blue URO sticker, and a URO logo laser-marked as shown in the above photo. Documenting the build and testing would be fantastic, looking forward to it!

well my new fan and motor assembly from URO arrived yesterday! so this will go in one of the fan housings that i have that will be rebuilt and sealed as soon as those parts arrive. I have one resistor pack that seems to be testing good , the other one i have to still figure out whats wrong with it before reassembly with the know stock oem fan and motor assembly, and the third one need a new motor so i ordered the brand new Bosch replacement motor to but into that fan, so 3 different ways to do this, depending on how deep you want to go, well even a 4th if you wanted to try and rebuild a motor but that does not appear to be possible on some of these according to how it looks from @Superhawy996 experiment turned out. he can confirm that, but the Fan/and motor assembly from URO is under $90. We just have to get the fan/housing seal, which 914rubber now makes, along with the flapper seals and seal for the lower fan to upper housing(diverter box).
Now if we could source a new or OEM NOS stock of resistor packs i could do a nice rebuild service with new seals, motor, fan and resistor pack.