A/C compressor not turning on

2003 CHEVROLET SILVERADO
200,000 MILES • 6.0L • V8 • 4WD • MANUAL
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CYC1OPSE
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I have read much of your information here and would just like to get a wiring diagram that is correct for my truck. I have tested a lot but would like to test more before getting into more details.

Please help me find a wiring diagram - for manual A/C controls. The fifth fan speed also normally will not work - could the compressor not coming on be related?
Nov 27, 2021 at 10:46 AM
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AL514
  • ✓Experienced Mechanic
  • 5,642 POSTS
Hello, below is the diagram for the manual A/C compressor circuit, I will post anymore I find that are relevant.
If you were wondering I think your fifth speed issue is either this Blower Motor Relay or the 40Amp Blower fuse. Because the only time the Blower Motor Relay switches over is in the fifth speed, here in pink on third diagram, for the other four speeds the relay stays in its rest position. The HVAC Control Module does the switching between the four speeds and then grounds the relay to switch over to the fifth speed as you can see in yellow.

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak
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Nov 27, 2021 at 12:38 PM
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CYC1OPSE
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I will check things out and let you know what I find. Thanks so much.
Nov 28, 2021 at 10:27 AM
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CYC1OPSE
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Thank you so much for your info AL W! It finally got hot enough here to make me get back on my A/C problem. The red wire on the high-pressure switch connector broke when I was trying to expose it to test it. It was very weak. Repaired the wire, tested the 3 wires based on the info you sent me, and problem solved, compressor working again. I will tackle the high-speed fan problem in a few days.

Thanks, you so much for the information you sent me.
Mar 20, 2022 at 1:15 PM
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AL514
  • ✓Experienced Mechanic
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Thats great news. Glad you got it going again.. If you need any other diagrams just let us know.. have a nice day...
Mar 21, 2022 at 1:58 AM
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