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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