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

[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.

[UROpartsman]

Awesome Phil, keep us updated!

[DRPHIL914]

@Mikey914
@Superhawk996

for superhawk, update on my 2 fans with testing the resistor packs, with new leads and cleaning contacts etc i get same readings for both of these, low medium and high are at or close to normal range. I think both are good, so i will assemble each in a cleaned up housing with new seals, one will hvae my brand new fan from URO and the other will have the new used one that tests good from Al Merideth, good free turning fan i bench tested it yesterday.

But @Mikey914 no care package no seal or rebuild kit has arrived, this project is stopped until i get the seals from 914rubber.

Mark, i will buy 2 additional kits too with all the seals including the new big fan to housing seal and the flappers seals and lower to upper housing seals., along with hardware.

If you can have the staff email me a paypal invoice i would like this sent out asap. thanks,

Phil

[Superhawk996]

@Mikey914

I have received a seal kit but wasn't able to get ahold of a seal for blower housing to the blower frame. Would really love to see you making these, that would allow for a total rebuild of foam seals.

Like @DrPhil914 . . . if you want to send me an invoice for a blower frame gasket, I'll glady pay to be the beta tester (IMG:style_emoticons/default/biggrin.gif)

[Superhawk996]

@Mikey914


for superhawk, update on my 2 fans with testing the resistor packs, with new leads and cleaning contacts etc i get same readings for both of these, low medium and high are at or close to normal range. I think both are good,

@DrPhil914

If you're getting similar readings between Medium and High Speeds, I'm thinking that your DMM is having resolution issues at very low ohm readings.

Might be time to upgrade the DMM. I'm always a fan of Fluke but let's be honest, that is big money for a hobby meter.

I've used HF meters with good sucess - not pro grade but not bad for hobby use. I consider them to be "burner" DMM's. I prefer the newer AMES unit.

https://www.harborfreight.com/dm1010-profes...eter-64021.html

I also have one of these around and found it to be OK but is sometimes a bit glitchy if you just turn it on and fly right to ohms settings. It sort of locks up intermittently. If you switch on, wait and then go to ohms, it's fine.

https://www.harborfreight.com/5-in-1-digita...eter-98674.html

I was maybe going to recommend an old school analog Pro grade meter but OMG . . . prices have gone way up. Price is now comparable to cost for a Fluke DMM.

https://www.grainger.com/product/1A587?cm_m...ASABEgKdKvD_BwE

Gold Standard Fluke

https://www.mscdirect.com/browse/tnpla/5243...BSABEgLxmfD_BwE

[DRPHIL914]

@Mikey914


for superhawk, update on my 2 fans with testing the resistor packs, with new leads and cleaning contacts etc i get same readings for both of these, low medium and high are at or close to normal range. I think both are good,

@DrPhil914

If you're getting similar readings between Medium and High Speeds, I'm thinking that your DMM is having resolution issues at very low ohm readings.

Might be time to upgrade the DMM. I'm always a fan of Fluke but let's be honest, that is big money for a hobby meter.

I've used HF meters with good sucess - not pro grade but not bad for hobby use. I consider them to be "burner" DMM's. I prefer the newer AMES unit.

https://www.harborfreight.com/dm1010-profes...eter-64021.html

I also have one of these around and found it to be OK but is sometimes a bit glitchy if you just turn it on and fly right to ohms settings. It sort of locks up intermittently. If you switch on, wait and then go to ohms, it's fine.

https://www.harborfreight.com/5-in-1-digita...eter-98674.html

I was maybe going to recommend an old school analog Pro grade meter but OMG . . . prices have gone way up. Price is now comparable to cost for a Fluke DMM.

https://www.grainger.com/product/1A587?cm_m...ASABEgKdKvD_BwE

Gold Standard Fluke

https://www.mscdirect.com/browse/tnpla/5243...BSABEgLxmfD_BwE

thanks for the recommendations, i will invest in a good one, i had a much better meter but it took a crap last year , need a good one with a good warranty

[Mikey914]

@Mikey914
@Superhawk996

for superhawk, update on my 2 fans with testing the resistor packs, with new leads and cleaning contacts etc i get same readings for both of these, low medium and high are at or close to normal range. I think both are good, so i will assemble each in a cleaned up housing with new seals, one will hvae my brand new fan from URO and the other will have the new used one that tests good from Al Merideth, good free turning fan i bench tested it yesterday.

But @Mikey914 no care package no seal or rebuild kit has arrived, this project is stopped until i get the seals from 914rubber.

Mark, i will buy 2 additional kits too with all the seals including the new big fan to housing seal and the flappers seals and lower to upper housing seals., along with hardware.

If you can have the staff email me a paypal invoice i would like this sent out asap. thanks,

Phil

Looks like I accidentally sent superhawk the care package
Please PM me your address and I can ship out tomorrow.
Mark

[Superhawk996]

@Mikey914
@Superhawk996

for superhawk, update on my 2 fans with testing the resistor packs, with new leads and cleaning contacts etc i get same readings for both of these, low medium and high are at or close to normal range. I think both are good, so i will assemble each in a cleaned up housing with new seals, one will hvae my brand new fan from URO and the other will have the new used one that tests good from Al Merideth, good free turning fan i bench tested it yesterday.

But @Mikey914 no care package no seal or rebuild kit has arrived, this project is stopped until i get the seals from 914rubber.

Mark, i will buy 2 additional kits too with all the seals including the new big fan to housing seal and the flappers seals and lower to upper housing seals., along with hardware.

If you can have the staff email me a paypal invoice i would like this sent out asap. thanks,

Phil

Looks like I accidentally sent superhawk the care package
Please PM me your address and I can ship out tomorrow.
Mark

@Mikey914
@DrPhil914

oops -- I can also turn it around and ship to the Doc.