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Climate Control 90 Q coupe

Here is a clip I have saved from a post a couple of months ago. Sounds right on.

> From quattro-owner@coimbra.ans.net Mon Apr 24 09:12:32 1995
> Subject: Temp Sensor Info
> Several months ago one of the outside temperature sensors (part of
> the heating/AC system) on my 1990 200Q failed.  The symptoms were an
> outside temperature indication that was always about 12 degrees lower
> than the true temperature.  I compared the resistance of the two 
> sensors at ambient temperature and found that the thermistor under
> the window read approximately 1000 ohms at 25 degrees C, while the
> front thermistor behind the grill read almost 1800 ohms at 25 deg C.
> Since these are negative temp coefficient thermistors and the control
> module always displays the temp of the coolest sensor, it was obvious
> that the grill sensor was defective.  A quick call to Audi and I found 
> that they would sell me a new one for only $95 + tax.  Being frugal,
> I characterized the temp -resistance relationship of the control module and of

> the working thermistor.  Steve Buchholz also provided  me with the temp - 
> resistance values from the Bently and they matched what I
> measured.  Bottom line is that I  found a thermitor from Digikey for
> approximately $2.00 that  replaces the Audi thermistor.  I  installed
> it this weekend and it works perfectly.  If anyone  has this problem, drop me 
> a line and I'll describe how to replace it.  The new thermistor mounts into 
> the old thermistor housing.
> Fred L. DeRoos
... boy, it sounds like the exact problem you describe!  As far as I know, 
Fred's address is <flderoos@mmm.com>, you might want to try dropping him a 
line ... Thanks Fred!