Date: 1 Jul 1996 12:50:52 -0400
Subject: Re: Stalling under pressure

   When the AC turns on, a solenoid is used to raise the engine speed via
   switching vacuum lines (I don't recall the details).  My guess is that one
   of those lines is leaking or off, and that when the solenoid closes you
   create a major leak.  Wild guess.

   On my urQ, the solenoid is on the passenger side near the coil.  It's
   mounted on a bracket on the firewall.

   >I do not wish to upset the Audi gods, but my frustration level is getting
   >there.
   >Car (87 CSTQ5) runs like a top and smooth as silk until I put the A/C on.
   >Then the idle begins to disintegrate and eventually in the heat, the car wi=

On later cars, I suspect the idle is controlled via the ECU and the idle
stabilizer...

For cars equipped with the dumb solenoid, you can easily make a "fast
idle" switch by switching the solenoid from "A/C" to +12. (Observation:
on my UrQ, the best the Factory Wiring can do is about 9.6 volts from
the A/C circuit, by switching to +12, I get about another 100rpm out of
it!). It should be worth about 100-250rpm, depending on the vagaries of
fate. (Another observation: it's not worth much on a cold engine, as it
is swamped by the "Aux Air Valve" effects, but as the engine warms up,
it does up the ante and speed up the cold morning warm up cycle). By
the way, do ***NOT*** just parallel the +12 switch to the solenoid, or
you will end up trying to feed the entire A/C circuit through your lit-
tle tiny switch and wire -- not good!

                                        -RDH