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Greg A.
Greg A., Master Troubleshooter
Category: GM
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Experience:  Working with Electronics & Cars for 25+ Years
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2004 gmc: 2500 hd..ACTIVATED, YOU DO NOT HEAR THE COMPRESSOR TURN ON.

Resolved Question:

i HAVE A 2004 GMC 2500HD SIERRA. A/C BLOWS HOT AIR. WHEN A/C IS ACTIVATED, YOU DO NOT HEAR THE COMPRESSOR TURN ON. BOTH FUSES CHECK OUT OKAY.
Submitted: 5 years ago.
Category: GM
Expert:  Greg A. replied 5 years ago.

Hello & Welcome,

 

Can you tell us if the refrigerant charge has been checked?

 

Have you opened the hood and verified that the compressor is not turning on?

 

Thanks

Customer: replied 5 years ago.
REFRIGERANT HAS NOT BE CHECKED. YES, THE HOOD WAS OPENED AND YOU CAN NOT HEAR THE COMPRESSOR KICK-ON.
Expert:  Greg A. replied 5 years ago.

OK - Thanks.

 

Here is the schematic for the compressor controls for the Manual AC system (Automatic will be similar).

 

graphic

 

You will notice that there is also a relay for turning on the compressor clutch, which is controlled by the PCM. You might want to try swapping that relay with another one that has the same part number (like perhaps the horn relay), or just giving it a "tap" with the handle end of a screwdriver to see if that turns on the compressor.

 

If there are problems with the pressure in the system, the PCM will not attempt to turn on the compressor. So I believe the next step would be to have the system checked for pressure and the possibility of a leak that has developed.

 

I hope this helps. Please let me know what you find or if you need more information.

 

Take Care, Greg A.

Greg A., Master Troubleshooter
Category: GM
Satisfied Customers: 5983
Experience: Working with Electronics & Cars for 25+ Years
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