My vw mechanic has checked the signals on the ecu & idle stabilizer:
throttle valve switch didn't close on idle. It was 91 DeutschMarks ($51)!
Now it works nice.

Conrad

>I recently had the same trouble arise where my idle would go up to about
>2000rpm when the A/C compressor was on.  There was one other person who
>wrote me saying they had the same problem, but nobody had figured out an
>actual fix.  I just disconnected the wire like you did.  I find my idle
>drops to about 900 when the compressor is on now- it normally is about 950,
>so not much change.  Perhaps you could increase your idle slightly to
>compensate until you figure out exactly what's wrong.  I've been thinking
>that the idle stabilizer control unit may be the problem, but haven't
>gotten around to looking at it yet.  I'll post a solution if I come across
>one
>