thanks for the inputs gents--interesting reading. My reading at the connector when attached and engine running is 1.25 volts or 2.5volts at 50% duty cycle as steve points out.

I hve placed full battery voltage accross the terminals of the idle valve and the idle REDUCED and eventually the engine STALLED.This sounds like the opposite of what Chuck was observing.

Chuck - did you introduce higher DC voltage with the ICU connected into the valve or just remove the connector and attached your vaiable dc there.

What input to the ICU determines the control current to be output to the valve ???I also note that when the AC in switched on there is no resulting increase in idle speed.

Thanks.