Re: Series Resistor Question '875KCSTQW

[Roland Broberg <broberg@cpg.mcw.edu>]

Paul F. Levine wrote:
> 
> Hello again,
> 
> I'm still trying to track down problem with the radiator fan now coming
> on a the lower speed. This seems to cause the car to get hotter than
> ususl and then eventually the fan comes on really high. I want to get
> back to "normal."
> 
> >From what I can gather, it may be either/both the thermoswitch on the
> radiator or/and the series resistor. I did try the AC with the engine on
> and it does work at low speed (lowest) then.
> 
> Anyway, if you have any thoughts re: your experience with failures,
> testing and difficulty/tips on self-replacement I'd be indebted.
> 
> Thanks to all. Actually, I hope to be able to help others at some point
> here if possible.
> 
> PaulJust finished this gem myself.  Took a week of pondering the shop manual on my 90 V8.  
Had the car for 2 years and don't think the electric fan had ever worked at any speed.  
Since summer finnally set in here in Milwaukee I decided that 120C was just too hot to 
run around town.  Shorting the hi speed relay caused the fan to run full speed.  
Swapping the medium and low speed relays had no effect-fan did not run with A/C on as it 
is supposed to.  Shorting the medium or low speed relays did not cause fan to run.  
Computer thought the fan was running!  Eventually found by running my hands along the 
cable from fan under driver side fender that when I reached the elusive series resistor 
and put a nasty burn on my finger-and the fan started running at low speed.  Hooray!  
Unfortunately the resistor could not been seen, even with a mirror.  Removed lf wheel 
and the wheel well liner which was surprisingly easy and there was this rediculously 
large resistor (70amp current) and the full power terminal connection was nearly burned 
off and quite corroded.  Removed the whole thing, put it in the vise, redrilled the 
terminal bolt. Reterminated the cables, clean, and soldered crimped some 
big-a** terminals on the approximately #8 wire and viola, I have a functioning fan and a 
happy V8!

My guess is that most of the Audis that have 3 speed fans will have the series resistor 
and are likely candidates for this type of failure.  The resistor draws a lot of current 
and also sits near the wheel and water splash to add to the problem.  Considering all 
the potential electronics that could have failed this was a no $ fix and, in retrospect, 
not that hard to find, given the symptoms.
Roland