Temperature gauge problem 84 4000SQ

[Stan Levine <slevine@shentel.net>]

I've been hoarding my silver 84 4000s Quattro. It has a little over 
50,000 miles. The car and its paint are in great shape because it has 
spent most of its life in my garage. Before buying it new I owned two 
other Audis: a 71 100 LS and a 76 Fox. The Quattro is by far the best car 
I've owned. One reason for the low mileage is a result of having a second 
car for casual use.

However, it started exhibiting intermittently high temperature 
indications a few years ago and then began operating normally for about 
two years. About a year ago the gauge began climbing close to the top of 
the scale every time the engine warms up. The radiator core is clean, and 
the temperature sensor and thermostat have been replaced without 
remedying the problem. The electric fan appears to be working properly.

The strange thing is that the fuel gauge is indicating properly. It is my 
understanding that the fuel and temperature gauges are powered by a 
voltage regulator, and if it goes bad both gauges will indicate 
improperly.

I am reluctant to use my Quattro because of the high temperature 
indication even though I believe it is a false reading. If it is due to a 
wiring problem, why does the gauge read high rather than low? Has anyone 
experienced a similar problem or have an insight into my problem? Any 
responses will be greatly appreciated.

Stan Levine
slevine@shentel.net