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Subject: Erratic temperature guage on 1991 Audi 100

<<Can anyone explain the following problem that I have with my 1991 Audi 100. 
<<After driving a mile or so from a cold start the temperature guage gets up 
<<to about quarter scale and then abruptly drops to zero. It stays this way 
<<until the entire coolant supply (including the radiator) has got hot. Then 
<<it starts to read correctly again. 
<<The symptoms would seem to suggest that the thermostat is opening early and 
<<staying open (doesn't make sense) - but changing it didn't help. With our 
<<current mild temperatures the problem is no big deal, but come January I 
<<can see me freezing to death. Any suggestions would be much appreciated. 
My initial thoughts are that your multi-function temp. sensor may be bad or
failing; it's the three or four wire sensor (pic at Scott Mockry's site
http://www.teleport.com/~scottmo/).  Try pulling off the connector.  If it's
full of coolant, or seems like the contacts are corroded, that's the likely
problem.  They can also look fine but fail internally... If all works
correctly when you put it back together, it's the sensor (I think they're
around $50? at thepartsconnection.com)
You can also feel the temperature of the coolant lines leading into and out of
the radiator to see if they're cold when they should be hot...
HTH, Chris Miller, Windham NH, c1j1miller@aol.com
'91 200q ==> http://members.aol.com/c1j1miller/index.html