Wiring diagram for relay for airconditioning - 2006 GMC Sierra

Does the A/C compressor engage ? Does the heater work ? Possible A/C compressor clutch if not turning on or A/C compressor clutch relay . Viewing a wiring diagram an testing the electrical circuits would be the way to find the problem .
The Trainer 40 When the compressor won compress

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There is a relay and a low pressure switch as well as a controller in the circuit.
You would need to backtrack from the compressor clutch to check for voltage in the circuit. You may need a shop manual to get the necessary wiring diagrams.

from fuse to relay from fuse to control panel from panel to ecm from ecm to relay from relay to clutch. from high pressure switch to ecm ecm to fan relays is how system works but dont remember wires .

To get a detailed electrical diagram, you won't find it free on the fixya.com website.

One would have to go to a place called alldata.com to find it, but will have to pay for the information.

If the freon is low there won't be power to the pump. If the pressure switch in the low pressure line is bad it won't run. Find the switch and unplug it and jump the hot wire to the ground and see if it will run. In other words if the plug has 2 wires cut a peice of wire and stick it in the plug. It temporally replaces the switch.

Look in the engine bay fuse box and see a square blue relay .swop it with one by it and try again if its ok you need new blue charging relay.

Its job is to cut the aircon relay off if the cars not charging so you dont get a flat battery but they go wrong.

I have the same problem, just started on a 2nd date last night. Wow, was that embarassing! Blinkers don't work. Hazards do work. Airbag light is On. Windows don't work. Radio is fine. Heater fan does Not work. Rear defrost button beeps but does not light up. I think it has something to do with the BCM. I have to go out of town for a funeral but will trace the wiring diagram when I get back and hopefully post a solution.
Really glad I found this site, thought the deceased's ghost invaded my car ;)