high idle W/ AC on

[Jonny-K5]

what controls the high idle function when you turn the AC on. my 89 blazer stopped doing this a few months ago. not sure if its a sensor, the computer or what?

 

[dyeager535]

Have to look at the wiring diagrams to be certain, but on most of GM's EFI setups, there is a pressure switch in one of the AC lines that the ECM monitors.