When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
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; Oct 9, 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.
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
Finding the 12v AC request wire: 70's GM 
