A/C no power from interior

2000 CHEVROLET SUBURBAN
240,000 MILES • 0.5L • V8 • 4WD • AUTOMATIC
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MECHANICALDAD
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I had my engine rebuilt. When I got it back the A/C will not come on (of course they did nothing).
Pressure switch seems functional. If I override the fuse/switch at the PCM the A/C works fine except drains the battery when I forget to turn it off!
I tried a different climate control board and no change. This has the auto temperature climate control board with rear air. May not be related but the rear defrost button next to the A/C button is not functioning either. To search the A/C wire can you give me the diagram? Also, to check the control board out of the vehicle with another harness how would I test the switch. Awful lot of questions here. Thanks
Aug 5, 2018 at 3:58 PM
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ASEMASTER6371
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Good morning.

What switch did you bypass and how? You may have damaged the PCM is you powered something wrong.

I attached a wiring diagram for you to view.

The PCM will ground the control side of the AC relay once it gets the correct signal from both the low-pressure switch and the high-pressure switch. You need to verify they are working correctly.

The high switch is normally closed and opens at 375 lbs.

The low-pressure switch is normally open and closes at 20 lbs of Freon pressure.

Roy
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Aug 5, 2018 at 11:59 PM
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MECHANICALDAD
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I just added a switch in place of the 8567 relay fuse.
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Aug 8, 2018 at 6:36 AM
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ASEMASTER6371
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Did you just jump 30 and 87 terminals? If you did, then you have no protection if the system pressures are out of spec.

Roy
Aug 8, 2018 at 8:15 AM
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MECHANICALDAD
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Yes that is what I did however, I did have a garage look at the specs prior to doing that. They also could not get power to the 30 and 87 terminals with the dash switch. I thought I could try to trace the wire if maybe the garage who replaced the engine damaged it somehow. I assume I need to check elsewhere first to see if when I activate the switch on the dash? I had a test light on the 30/87 terminals but thinking it looks for power somewhere else before it activates that terminal? Yes/no?
Aug 10, 2018 at 7:18 AM
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ASEMASTER6371
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Okay.

The power to 30 comes from the fuse block only, not from anywhere else. 87 becomes hot only when the control side of the relay grounds.

You need another shop that knows how a relay works and can find the issue for you. It sounds like your guy does not know how the system works as well as a relay.

Roy
Aug 10, 2018 at 2:03 PM
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MECHANICALDAD
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So just to finish this story we needed to replace the compressor and in doing so we found that when the mechanic who rebuilt my engine was in such a hurry to finish the job he jammed the connector on the high cut out switch and folded the pin over. Since you cannot access this without moving the compressor the mechanic told me it was good since when we over rode the fuse the compressor turned on. Thank you for all your help in this.
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Sep 19, 2018 at 7:06 AM
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ASEMASTER6371
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You are welcome.
Sep 19, 2018 at 7:28 AM