AC compressor clutch not getting power
b.benz at charter.net
Thu Aug 18 16:56:42 EDT 2005
Ben, do you have a Bentley? Go to the schematic on pg 590 and note that
the AC Clutch relay is home at position #1 in the Aux relay panel, not in
the fuse panel. This relay has 2 failure modes, BTDT. An open supression
diode causes big negative voltage spikes superimposed on the electrical
system when the clutch drops, radio popping. A shorted diode causes the
clutch to run all the time when the AC is on. The diode is replaceable.
Check for X Bat voltage to the relay.
> Reply-To: Ben Swann <benswann at comcast.net>
> Date: Thu, 18 Aug 2005 15:11:15 -0400
> To: <quattro at audifans.com>, <200q20V at audifans.com>
> Cc: brian at intramalls.com, Ben Swann <benswann at comcast.net>
> Subject: AC compressor clutch not getting power
> Two '91 200Q20V sedans with apparantly the same problem. The AC system has
> full charge - approximately 90PSI static/35PSI low and 180 PSI high
> pressure side during operation and outside temp around 80 deg. F. Climate
> control set to low and everything operates except for compressor clutch is
> not engaging. Applying power directly to compressor engages clutch and
> system blows nice and cold.
> I noticed on the one I was just working on that there was no relay in
> position number 6 where the fuse box cover indicates AC relay should be.
> Inserting relay makes no difference.
> Any clues as to what is going on? BTDT on common culprit(s)?
More information about the 200q20v