> The connection to my AC Compressor is a White wire with a Green stripe, and
> that color wire is not on your list.
>
> Have I got the wrong wire? If not, where does this White/Green lead to if
> not the Idle Controller.

Oops. I left that one off the list. Yes, the WHT/GRN wire from the
idle controller connects to the RED/BLU lead powering the compressor
clutch.

> Another question I have is WHY ME?!  Noooo, the question: This White/Green
> wire has a connector on it, but the SD508 has no place to connect it, so I
> have spliced into the AC Clutch on wire. Did any of the compressors come
> with a cicuit built in with a diode or something, that I might be missing?

According to the Bentley page on AC wiring (97.141), it's a straight
wireup from the compressor clutch: 12v to the clutch directly into the
WHT/GRN lead

One diagnostic you might try is to disconnect the WHT/GRN lead and see
what idle does when you apply 12v directly to it from the alternator,
without activating the AC compressor clutch. If the idle still hunts
all over the place, you know it's not mechanical issues with the AC
compressor. From there, the trouble has to be in one of three places:
controller, valve, or the wiring that feeds them. You've already ruled
out the controller. If you have a spare idle valve (or even one on
another van) they're pretty easy to swap. Wiring issues are probably
the hardest to find, given where the wires run.

--
John Bange
'90 Vanagon - "Lastwagen"
'90 Vanagon GL - "Wiesel"