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I'm trying to make sure I am using the right 12 volt AC request wire to add to pin 17 for the AC. I tried to explain it but it was too confusing so I copied the wiring diagram below. The green wire is what I believe to be the AC request wire. It was wired to the original solenoid that used to idle the car up when the AC was turned on, but it also has some splices coming off of it. Also, this model Caprice had a "diagnostic system" installed from the factory on the wiring, which basically just adds a whole lot of extra wires and confusion to the diagrams. The blue wire goes to what is labeled as the "Ranco Cycling Switch." Is this what they called the high pressure switch for the AC?
I know that typically you would tap into the wire that feeds power to the original AC compressor, but in this case that wire goes into pin 66, then back out to the high pressure switch, then out of the high pressure switch on pin 59, then through another connector on pin 59 in the AC harness connector, then onto the compressor. Since I'm eliminated the original high pressure switch and rewiring it, couldn't I make it easier by using the wire goes to the fast-idle solenoid (labeled idle stop solenoid in diagram) and get the same effect?
Last edited by Vetteman61; 10-09-2018 at 10:45 PM.
The cycling switch is a low pressure switch mounted on the accumulator, the older systems didn't have any high pressure protection, just blow off valves. The easiest way to wire it would be to take the wire that originally went to the compressor and use that. By that I mean the wire coming off the switch in the dash, not after the cycling switch or it will turn on and off as it cycles.
Based on the wiring diagram you could tap into either the green or blue lines (both marked "18 LT GRN") since they both connect to the selector switch and get a constant +12v signal any time the selector switch is in an "AC" type mode. You would not want to connect to the "18 DK GRN" which is the cycled 12v going to the compressor clutch.
10-09-2018, 10:23 PM
Finding the 12v AC request wire: 70's GM 
