custom swap, trying to figure out the AC. I both plugs going to the compressor have 12v

[nicklatech]

pin 85 on the AC relay isnt going to ground. Once I ground that wire the relay fires off as expected.

 

[Black_cirrus]

What's the base truck you're working on Again?

 

[nicklatech]

its a 1999 GMC serria c2500 SLT that originally had a 5.7l engine.

I found this schematic for a 1995-1998 gm truck, but I dont think its correct for my truck. I think I have 3 pressure switches. There is one on the back of the AC compressor, one on the accumulator, and one on the AC high port.

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[nicklatech]

I found this simple diagram online. If I cant resolve this issue then I plan on rewiring the AC system to match this diagram located here

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.

 

[Black_cirrus]

If I read that diagram right relay should be should be constant ground and voltage switched... I have access to alldata at work but not much time to use it. I'll try to check on there.

 

[Black_cirrus]

So if I were you I'd wire it up like the 98 diagram... I didn't watch the video. But here's the diagram. Shows 85 is direct from pcm. I highlighted for easy ID.

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[nicklatech]

So if I were you I'd wire it up like the 98 diagram... I didn't watch the video. But here's the diagram. Shows 85 is direct from pcm. I highlighted for easy ID.

I dont know if I mentioned but I no longer have a PCM since I'm running a mechanical diesel with a stand alone 4l80e transmission controller.

Currently, I wired the 85 to a grounded toggle switch. But the system doesnt seem to have the sensors wired directly into AC like the older trucks from 1998 and back. Is it possible you can get a picture of the entire view of the diagram? I would like to see how the system worked originally. If you dont have time, that is OK. What you have posted helps me understand that the PCM is the current reason my AC system isnt work properly.

Thanks!

 

[Black_cirrus]

Yea I know you have no PCM, that's why I said I'd wire like the 98 diagram you posted. I printed both pages of the diagram already so here you go

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[nicklatech]

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I have it wired up the three sensors in series, but there the above sensor is the only one that is not working. I have tried two of these guys so I think its something I'm doing wrong. I tested with the sensor disconnected and connected both showed no connection. I can jump the harness to that plug and the compressor fires right up so I think I have it wired correctly unless that sensor doesnt work the way i think it works. The other sensor on the accumulator and the back of the compressor work as expected.

 

[Black_cirrus]

What are the wire colors?