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

[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

[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.

[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!