Electronic climate control playing up

Peter Golledge petergolledge at gmail.com
Sat Mar 14 18:48:00 PDT 2009

If resistor gives the right value at the source I'd suspect a short or extra
resistance in a connector or the wiring.  If the sensor is NTC then suspect
a short, if the sensor is PTC then a bad connection is likely the fault.
Try disconnecting the sensor and see that the CC head thinks the temp is

-----Original Message-----
From: quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com] On
Behalf Of Dag Bøsterud
Sent: Saturday, March 14, 2009 5:02 PM
To: quattro at audifans.com
Subject: Electronic climate control playing up

I have a very late 1990 Audi 100 Turbo Quattro Sport Exklusiv on which the
climate control has started playing up.
The problem seems to be that the climate control system seems to believe
that the temperature in the car is lower
than it actually is, thus always blowing hot air. If I set the system to LO,
it blows cold, because the system doesn't
care about input from sensors when in LO. Since my car is a very late 90's,
the dreaded bowden-wire is gone,
and my climate control system uses the same temperature control motor as the
new climate control system
that came out for the Audi 100/S4 (C4-cars) in 1991 and the V8 in 1992.
This time, the little motor is not at fault :)

I've done a bit of fault finding using the systems fault diagnostics, and it
seems that the sensor mounted on the roof
is somehow giving the wrong values, although with an ohm-meter it measures
okay - at least according to the Bentley

So.. any hints, tips or clues?


'90 100 TQ Sport Exclusiv
131 000 miles

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