> The AC compressor engaging sends a signal to the ISCM and increases idle
> speed a bit when the throttle is closed (assuming the throttle position
> switch is actually closed).

I think the ISCU just notices the drop in RPM from the AC and
compensates for it.  The only thing connected to the ISCU in
that way is the power steering pressure switch.  See Bentley
97.107.

The AC is 97.140 & 141 and there is no connection back to
the ISCU.  The only thing the AC relay tells is the radiator
fan--to kick on low speed, at least.

Richard
'87 Syncro Westy without a waterboxer