MFTS/Temp gauge

Alan Lubow alosteo at qwest.net
Tue Mar 8 14:55:07 EST 2005


Thanks for all the responses on my question about the non-functioning temp
gauge on my 1994 90 Quattro a while back.  Thought I'd share my experience:

I took my car up to my local independent Porsche/Audi mechanic.  He sold me
a
new sensor for $75 , and  showed me how to put it in at no extra charge.
(Said
he'd usually charge an hour of labor, but I've been a regular customer for
years, having him work on my 911s).  I wouldn't have known where to find the
thing -- on my car it's at the top of the motor, in the back, on the
passenger side.  That seemed
to help initially.  The gauge worked properly and the car ran better --  for
about a day.  Then the same condition recurred.  No action on the gauge at
all and poor running.  My understanding is that the sensor tells the
computer what temp the engine is running at, and it responds with more or
less fuel accordingly.  So I was probably running too rich most of the time.
I called my mechanic and was told that the wiring might be bad.  "We
usually have to cut the old wires back past the corrosion and then run
jumper wires to the sensor,  bypassing the plug."

My four terminal plug showed no corrosion but wasn't in the best shape (the
plastic
had cracked on two sides).  I went to the junkyard and found a better plug;
also found that these sensors are used on many other Audi models besides
mine.  Usually they are in the front of the motor, on the driver's side, and
upside down.  Apparantly in this configuration the sensor is much more prone
to corrosion.  I found several with their boots cut open at the end to allow
for drainage, and corrosion of the wires seemed to be pretty common.  I
found one where the wires had been modified with jumpers as described by my
mechanic.  The sensor on that one looked brand new, so that's the one I used
in my car.  And, it fixed the problem!  So, I guess the new sensor my
mechanic sold me was bad out of the box!

Hope this helps someone else.  It sounds as if this is a fairly common
problem with these cars.

Alan
Denver, CO






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