Hey Gents!
I have a basket case 1984 944 that I have saved from the scrap yard..... She ain't pretty, but I got her running after a eight year nap! Been having a ball driving her! A couple of months ago I turned on the defroster (or is that "demister" in the Porsche world?), and the switch was bad and would not turn off.... To compound this excitement..... My cabin began filling with smoke! After feverishly pulling relays till I got the right one I limped her home..... I come to find a mouse nest within my blower motor! I got lucky that I didn't burn the whole car down!

I replaced the switch and found a used blower motor..... Dropped 'em both in and they worked fine..... For a time.... I think at some point the three lowest speeds stopped working.... Leaving only the fastest
Setting.... Well last week, that crapped out too.... So no defroster just in time for winter!

I jumped the blower directly from the Battery, and it ran fine..... So
I'm guessing it is the resistor that is bad.... The trouble is..... Since this is an early car.... I can't find one to replace it..... I have read that
Soaking the resistor in white vinegar may solve the problem.... Can I do so right on the car..... I would rather not cut the four wires to it, if I don't have too!

Thanks!
Fred

P.S. Since this is an early car with the separate defroster and a/c switches.... I have read that there is an "A/C cut off relay" could this be my issue? I own a multimeter..... But really have no idea how to use it!

 

The defroster switch is for the rear window, and has nothing to do with the blower. The only way to defrost the windshield on an early car is close all the dash vents and slide the rightmost slider to the right.

If the A/C cut off relay was stuck the A/C blower would run but the fresh air blower wouldn't on any setting, or vice versa. Considering you're saying the fresh air blower doesn't run at all it's possible this has failed. Located behind the glovebox.
Part number is 171959141. NOT 171959141A. Ending in A is a different relay entirely.

The fresh blower on the fastest setting should be bypassing the resistor. If it doesn't run on max, the issue is somewhere else.

Diagnosing climate control issues on an early car is a lot of fun, since even the service manuals have relays mislabeled in the wrong locations.

 

Hey Mistax!

You sir are the man! I found the relay you mentioned...(really Klaus...what ya got against me???) . Can't really tell if it is bad or not.... I tried plugging in a couple of generic relays.... But got no responce...... I'll order one and see if it makes a difference..... $13. + $15 shipping...... Sigh.... Story of my life!

Just for fun.... What does the larger relay # 94461511300, next to the one you mentioned, do?

Im one of those lucky souls who's fuse/relay panel does not seem to match the diagrams I could find online.... Makes everyday an adventure!

Thanks much!
Fred

 

The second relay is for the entire air conditioner system, and auxiliary radiator fan. It's the same relay as the main radiator fan relay. Current modern version part number is 94461511302.

If the A/C blower works, and the aux fan comes on with it, then that relay is functioning properly. When mine failed the A/C blower wouldn't work, compressor wouldn't engage, etc.

There is a fresh air blower relay on the main relay panel under the dash. That could also be an issue. I don't know the part number of that relay, I'll check on my car if you need it.

Since you said there was smoke, your problem is probably going to be more than just a relay. I would recommend dropping the entire fuse block and relay panel and inspect the wiring.

Realistically I doubt the interlock relay is the cause, but replacing it isn't going to hurt.

Which relay did you pull out when it happened?