Defeating the AC idle compensation on the BMW E34 M5:
In order to get rid of the annoying surge when the AC cycles on/off in my car, I disconnected the feedback signal between the AC compressor clutch and the DME control. The engine idle speed control is more than adequate to maintain idle speed under the changing load condition. Any residual idle fluctuation will settle down after the system "adapts" to the new conditions.
I have had no problems with this mod on my '91 US spec 3.6; however, as they say, YMMV…
Bottom (chassis harness) view with pin numbers:
2. Simply cut this wire as shown, and apply a small piece of heat-shrink or electrical tape to the cut ends. Cut far enough from the connector in case you want to reverse the modification in the future.