A/C Clutch not engaging

Discussion in 'General Chevy & GM Tech Questions' started by promod, Jun 3, 2010.

  1. promod

    promod New Member

    Wondering is there is a test procedure to determine why the A/C clutch will not engage.

    2002 Silverado 3500 LT

    Symptoms: No cold air, A/C light on dash will light, fan door appears to work from dash to foot to mix to defrost positions.

    Known: Freon charge is good, fuses (inside drivers compartment and under hood) verified good. Swapped out relay with another with no effect.

    Thanks for any help on this!
  2. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Have you jumped the low pressure switch???
  3. promod

    promod New Member

    I haven't done that yet. If I do and the clutch still does not engage, what would be the next step? Trying to gather as much information as possible before I have to start then stop.

  4. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Sorry also jump the high pressure switch.. IF the still doesnt engage it then you need to run power directly to the AC compressor and see if the compressor engages then. If the Compressor doesnt engage with direct power from the battery then the Compressor is shot.
  5. promod

    promod New Member


    A couple of questions, the low pressure connection is on left side of the accumulator correct? Where is the high pressure switch? Would you suggest jumping both of these at the same time? A paper clip would probably do the trick I would think.

    Also, how should I connect power to the compressor? There is a plug on the front/top of the compressor, I would assume this is where I would provide the 12V.

    Pull the plug and connect 12v + to where and negative to where? I can pull the power from the front left battery.

    Thanks again for your help!
  6. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Yes the low pressure switch is on the side of the accumulator, the High pressure switch loos very similar to the low switch and is on the lines somewhere i cannot recall at this exact moment. And yes you can jump them both at the same time though i would do them individually so you know which switch is shot.. if not both of them. And yes the plug on the compressor, and power from the battery with the motor running (you most likely already knew that i actually messed this up a while back when i got in a hurry)
  7. promod

    promod New Member

    If I understand correctly, I will connect one side of the battery (positive) to one side of the compressor and the other side (negative) to the other?
  8. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Yep.. just take a look at the harness plug (since there should be 2 wires) and remeber that the black wire is ground.. And the color wire will be your positive.
  9. MightyMax

    MightyMax Rockstar 100 Posts

    As stated, make sure the pressure switch on the accumulator is good.
    Those switches are cheap (was for my truck, $5.00 I think).

    Take a wire and run from the + terminal on the batter, and stick the other end into the power harness on the compressor. This should engage the compressor and the clutch.

    Something you can do before jumping these guys, just to do an easy test first of all.
    Is get some guages and check the pressure.
    Since the A/C is not coming on, you should see pressure in the lines.
    Even pressure on both High and Low sides, maybe about 50 - 100 PSI
    This will confirm that you do have a sealed system and there is freeon in the line.
    Simple and easy check.
  10. promod

    promod New Member

    The pressures have been checked and verified that they are where they should be.

    I will assume that the jumper wires from the battery are going to go to the compressor itself, not the plug that is disconnected from the compressor correct?

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