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Short cycling AC with correct chaarge on a 2013 GMC Sierra Denali 6.2L AWD Auto

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  • Short cycling AC with correct chaarge on a 2013 GMC Sierra Denali 6.2L AWD Auto

    A/C cycles on for about 5 seconds then shuts off for a minute. Can't seem to pinpoint the problem. I thought maybe it was low so I evacuated the system to have a fresh starting pont.

    System evacuated, pulled vacuum for 30 mins, let it sit for 30 mins to confirm vacuum didnt bleed off, recharged with 25oz of R134. The compressor didnt want to turn on when adding the R134A so I manually bridged the A/C relay to force it to drink the R134A. While I had it bridged the A/C was nice and cold.

    Same issue as before I did the recharge. The A/C cycles on for about 5 seconds then shuts off for a minute. So on and so forth.

    I've swapped the AC rely with the fog light rely and still does same thing. No stored codes or anything...............Bad pressure switch? Bad air temp switch?

  • #2
    Are you sure of that charge amount? Can't look that up you would go by an original sticker stating that if it's original. Still cycling no codes. This is so computer controlled you don't have access to the dealer side codes nor do I. Jumping anything is wildly AYOR I think system is trying to default to OFF for a reason to many to list why a compressor shouldn't be engaging not just A/C problems at all.
    Tom
    MetroWest, Boston

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    • #3
      Ok, I pulled up the vehicle on Rockauto to see what kind and how many pressure controls the vehicle has. If it can be believed it has THREE! a low pressure and high pressure switch at the compressor and a pressure transducer that I assume is on the high pressure discharge line
      Without the benefit of a manual or wiring diagram. I would guess that there are low and high pressure safeties (cut-outs) and a pressure transducer for operational control by an ECM
      Under no conditions "jumper" a three terminal transducer, as you will do serious damage.
      If you want to take a stab throwing parts at the problem, the three terminal pressure transducer might be worth trying. According to Rockauto it can be had for less than $30 and all three electrical switches/transducers can be replaced for under $60
      If that doesn't solve the problem, than You'll need someone who can pull codes and read why it is shutting the system down.
      Last edited by Cornbinder89; 07-17-2018, 05:21 PM. Reason: location of the transducer

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      • #4
        Two likely reasons: 1) a faulty trinary switch 2) a faulty evaporator temperature control sensor.

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        • #5
          Thank guys. I can see the evap temp sensor and the low pressure switch but not the high pressure switch. Im gonna start with the low pressure one. Amazon has it for a bit more with prime.

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          • #6
            Check to see if there is a "hidden" stored code in the ACM. It may be a "BCM1347" or "BCM1358". Be sure BOTH radiator fans are running. Do a water spray test on the condenser.
            Tight Lines!
            Ed

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