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

[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]

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.