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Discussion Starter #1 (Edited)
My AC hasn't worked for a couple of years. Last year I thought maybe it was low on freon and tried to charge it but that did nothing. This year I have gotten some gauges to hook up to it. After hooking them up they read dangerously high on the the low side and low on the high side. I used a wire from the positive terminal to the compressor to turn it on. That made the low side drop to low and the high side come up some but it still wasn't blowing cold air. After turning the compressor off it went back to dangerously high on the low side and low on the high side. I jumpered the pressure switch with no luck. I also jumpered the thermocon (blue/green and blue/white wires) with no luck.

I checked my voltages on the pressure switch and got just over 5v and the same for the thermocon. So then I started checking the relays, they both switch on when I hook them straight up to the battery so they are good. Then I started checking the voltages at the relays. The AC relay test 12v across yellow and blue/green, and 5v across blue and green. The AC cut relay however tested 5v across yellow and blue/green, and ONLY .12v across green and green/blue.

Now I only have enough electrical skills to be dangerous so correct me if I'm wrong but it seems to me the problem lies in the low voltage to the cut relay since it is a 12v relay and is only getting a 10th of that. According to the wiring diagram which I will attach, the green wire goes to the main relay and the green/blue goes to the ECM.

Any suggestions? Bad ground? Bad ECM? Bad something that tells the ECM to turn the AC on?

FYI the AC button light stays on, it does not blink or go off at any point.

Just tested the pressure switch, it gets no power unless I jumper the thermocon. Also if I was to hot wire the compressor and the condenser fan it should work regardless of any electrical problems, correct? That would allow me to rule out mechanical and isolate the problem to electrical right?

Ok, with the compressor running I'm getting 12 and 110 on the low and high side, with the compressor off I'm getting 83 and 90 on the low and high side.

Update: After putting freon in the system it blows cold air but only if I hot wire the compressor and condenser fan. If I don't hot wire them they don't come on. Any suggestions? Sounds like an electrical problem for sure now.
 

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I checked my voltages on the pressure switch and got just over 5v and the same for the thermocon. So then I started checking the relays, they both switch on when I hook them straight up to the battery so they are good. Then I started checking the voltages at the relays. The AC relay test 12v across yellow and blue/green, and 5v across blue and green. The AC cut relay however tested 5v across yellow and blue/green, and ONLY .12v across green and green/blue.

...

Update: After putting freon in the system it blows cold air but only if I hot wire the compressor and condenser fan. If I don't hot wire them they don't come on. Any suggestions? Sounds like an electrical problem for sure now.

Recommend correcting the discovered / identified issue of low voltage between the (Main Relay) and A/C Cut Relay trigger (*Green wire),

Without correct (+) on the trigger side, the A/C Cut Relay -> will never engage the A/C compressor clutch,

HTH & Regards,
GottaCruise
 
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