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  1. #1

    Default 1999 C2500 A/C clutch doesn't disengage

    I just changed the compressor, accumulator and dryer and recharged the system. Also, just had the air inlet actuator replaced. I noticed the compressor (clutch) never stops spinning, regardless of what fan speed and/or how cold it may be in the cab. Could the culprit be the switch that is located on the accumulator? I've heard it is called the low psi switch, and/or, the clutch cycling switch. Any assistance would be appreciated. TIA James

  2. #2

    Default

    Well, replacing the switch located on the accumulator doesn't seem to cycle the compressor clutch. Maybe if i begin from the day i purchased the truck, this might help diagnosing the problem. I bought the truck about 5 weeks ago (early June). During a trip, the vents began blowing warm air and we noticed condensation forming on the blower housing and water beginning to drip on the passenger floor mat; I assumed the evaporator was icing up, and/or, the drain tube (out of fire wall) may be plugged. turning the AC knob on and off the entire trip was necessary to stay somewhat cool. The next day (after a 300 mile trip) took truck to a mechanic and he said the compressor was shot. Went to O'reillys and bought a new (not used) Murray compressor, accumulator and orifice tube. Mechanic installed it and drove it and said it was working satisfactory, but, did tell me the re-circulation door wasn't operating and that it could be in the control head. I told him i would look into it.


    We drove home a couple of days later and the truck was cooling much better. However, there was still condensation on the blower housing and puddling on the floormat. I assumed this was because the system was trying to cool incoming 95degree air and not cabin air, or, there was still some pluggage. Fast forward to last week, i had the actuator replaced on the air inlet door. Definitely could tell the difference while driving around in town, and, i never noticed any condensation develop on the blower housing. I figured the problem was fixed.


    Last Wednesday, we made the same 300 mile trip to visit my wife's parents. Everything seemed fine, but, close to our destination, i noticed the passenger floor mat was a little wet. I also noticed the condensation again on the blower housing. The next morning, i popped the hood, started truck and turned the AC on, cranked on high. Within a 20 minute span, i realized the clutch never cycled off; it just stayed spinning. Still not knowing exactly what this switch did or was called, i replaced it with one from NAPA. This still did not allow the compressor clutch to cycle.


    On the way home this past Saturday, the AC ran fine; however, there was still condensation around the blower housing and some dampness on the floor mat. With what i've just posted, does anyone have any ideas what i should check for next?? I'm short on funds and don't really want to take it to a mechanic unless i absolutely have to. Any help at all would be greatly appreciated. thanks, James
    1999 Chevy LS Crewcab 2WD (OBS)
    5.7, 4L80E, GT4/G80

  3. #3

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    Sorry, I didn't see this thread when I answered your question in an other thread ( http://www.gmtruckclub.com/forum/sho...antly-spinning ). I must confess, I did not read all of the info on your 2nd post, so my answer may be wrong. but, check the relay anyway.
    Ray

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  4. #4

    Default

    Ray, last evening, i swapped the relays and this did not solve the problem. I let the truck run at idle for some time, playing with the fan and temperature settings; although the cabin was very cold, the compresser clutch would not disengage; I also noticed there was quite abit of drainage coming form the evaporator drain tube, more than what i think should be the norm. With the truck running and the AC on, i pulled the connection immediately at the clutch and it stopped rotating; i plugged it back in and it began spinning. Also, i noticed the discharge line (from compressor to condenser) was quite hot, to the point i couldn't keep my fingers on it. Not sure if this is normal either. The low side line leaving the accumulator and back to the compressor was cold and sweating, as i would expect it to be.


    I took a photo of the compressor with my phone but cannot figure out how to attach; when i do, i will. This is a new compressor i bought from Oreilly's; it is a Murray. Anyone know what my next move should be?? thanks, James

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    Here's the compressor. I have never seen a clutch face such as this. It looks like the three biscuits are are attached and cannot be removed. Also, i failed to mention earlier that the gap (or clearance) between the clutch plate and pully is very minimal; I didn't have my feeler gages but would say it was around 5 mils. Also, just left Oreilly's and had them produce me another Murray compressor. This compressor didn't have the same clutch face, but, the gap was very similar to the one i have. Could this be a clearance issue, keeping the magnets from releasing? thanks
    1999 Chevy LS Crewcab 2WD (OBS)
    5.7, 4L80E, GT4/G80

  5. #5

    Default

    If pulling the electrical connection at the clutch disengages the clutch, the compressor and it's clutch are good.

    You have an electrical problem downstream.

    If you pull the clutch relay (while it's running), will the clutch disengage?
    Ray

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  6. #6

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    Ray, i haven't done this yet but will when i make it home this evening and get back with you. I only saw one A/C relay in fuse box under the hood and will pull this one to see what happens. thanks, james

    Alright, i pulled the relay and the clutch disengaged; plugged back in, started up again. Not sure where to go from here but to another AC mechanic. Any suggestions? TIA
    Last edited by cookj; 07-10-2013 at 06:02 PM.
    1999 Chevy LS Crewcab 2WD (OBS)
    5.7, 4L80E, GT4/G80

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