GMC Suburban:

A/C compressor will not disengage

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# 1  7/30/2015 6:18 PM

koecher
New member
Registered: 7/30/2015
Posts: 1

A/C compressor will not disengage

2002 Suburban.

A/C  works good but A/C compressor clutch will only disengage when system turned off.  Whenever fan/blower motor engaged regardless of whether heat or vent, the A/C compressor clutch is engaged. This is true even if the  A/C button is not depressed and system not in defrost. 

Is there a A/C cutch relay that may have gone bad  that could cause this  problem ? 

Let us know. thanks and best regards.

Koecher

Last edited by koecher (7/30/2015 6:19 PM)

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# 2  7/30/2015 11:38 PM

TechHelp2
Administrator
Registered: 11/24/2009
Posts: 1313

Re: A/C compressor will not disengage

You need to check a few things first before you condemn the A/C relay.

Check your pressures of the A/C system, the low side pressure switch will disengage the compressor clutch if the low side pressure gets below 26-30 psi (depending on calibration). If it stays above this number the clutch won't disengage.

Check the ambient pressure chart to see low side pressures depending on outside temperature. This can also help in diagnosis.

If you have a scan tool you can check the command of the A/C clutch to see if it is electrically turned on by the PCM. If it shows it is supposed to be commanded on it will say so. If it shows the clutch command to be off go to the A/C clutch relay and pull it out and see if the clutch disengages. If it does disengage replace the relay.

The A/C clutch relay is in the under hood fuse panel. I am also enclosing a wiring schematic for the A/C compressor clutch circuit and also the ambient temperature chart. Hope this helps. Get back to me if you need more help diagnosing this problem.

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# 3  7/31/2015 2:45 AM

Administrator
Administrator
Registered: 9/27/2008
Posts: 1296

Re: A/C compressor will not disengage

It's a good idea (if a good scan tool is available) to see if the compressor is being commanded on. But if you notice on the schematic, the 10 amp AC fuse which actually powers the compressor clutch is hot at all times. So if the relay was stuck on, it would not disengage with the system turned off. As a matter of fact, it would stay engaged with the ignition off and kill your battery overnight.

Double check your controls. Sometimes there's a max AC button which might keep the compressor engaged regardless of the other settings. If there's an ON light on the AC button, does it go on and off, or stay on regardless when the button is pressed? That button is there strictly to turn the compressor On and Off manually.


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