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Thread: 5.3 swap, ac not working

  1. #1
    Join Date
    Jul 2018
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    5.3 swap, ac not working

    Jl8806's AvatarJl8806 , Today 07:29 AM
    I'm almost finished with my 5.3 swap into my 97 chevy k1500 but I'm having a little trouble with the active. I'm using my 97 compressor in the stock location, the engine is a 03 with a 01 tb, harness and 0411 pcm. I have power coming from the switch on the compressor to the pcm requesting ac but there is no power coming out of the pcm to activate the relay, anyone have any ideas? Thanks for any help

  2. #2
    Join Date
    Nov 2009
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    SAN ANTONE
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    778
    do you have any pressure sensor hooked up going to he ecm
    06 rcsb, 6two, 231/235, 4.11, pacesetter, 80e, 14 bolt, Nelson tuned
    2011 rcsb 6two swap in the works with 6l90 and boost
    FARMTRUC CAN GARGLE PEANUT BUTTER

  3. #3
    Join Date
    Jan 2012
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    warwick ny
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    Pin 55 on red connector if your using a truck pcm connects to pressure switch. You can do a quick test by grounding pin 55 so it works. The a/c request won't work until pin 55 is grounded or when connected to pressure switch and has pressure.

  4. #4
    Join Date
    Sep 2018
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    It's a little more complicated than gagliano7 is making it out to be.. There is a low pressure switch, a high pressure switch, and a high pressure recirculation switch. Then there is the Compressor clutch relay, and also 4 wires that have to be run back to the PCM. REd 17, REd 11, Red 55, Red 43. Then you have to figure out where, and which wire, coming from the HVAC controller to hook to the high pressure switch. I'm battling through it right now on a GMC 1500 LS swap. That's how I found this post. Hoping there was more information to help me resolve it.. But... I see you are in the same boat as I am.. Still searching..

    OP States; "I have power coming from the switch on the compressor to the pcm requesting ac but there is no power coming out of the pcm to activate the relay," Okay, the switch on the back of the compressor is HIGH PRESSURE switch. Unless I'm misunderstanding what you are typing.. THAT is the switch that sends the signal to pin 17 on the RED connector.

    Are you testing for this signal with the engine running? The PCM will not command the compressor clutch relay to energize unless the engine is turning at least 550RPM. Also, you said "there is no power coming out of the PCM to activate the relay". There SHOULD NOT be any power coming out of the PCM to power the relay. The PCM provides a (-) GROUND to the COMPRESSOR CLUTCH RELAY to activate the compressor. Pin 43 is the COMPRESSOR CLUTCH RELAY CONTROL WIRE and should be a GROUND (-) when the PCM wants the compressor to run. If you want to see if the problem is with the PCM, or the wiring feeding the PCM, then start the engine, let it idle, and then cut back some of the insulation on the wire coming out of PIN 43 on the red connector, and then touch it with the end of a grounded wire. If the compressor kicks on when you ground that wire, then you know the problem is *most likely* the wiring, or one of the switches that feeds signals to the PCM. If the compressor still does not kick on when you ground that wire, then look at the compressor itself. DO NOT run the compressor with the ground wire for more than a few seconds as you can damage the compressor permanently if it is low on freon.
    Last edited by Kawabuggy; 10-07-2018 at 11:54 AM. Reason: add information

  5. #5
    Join Date
    Sep 2018
    Posts
    4
    Just found this; https://www.lsenginediy.com/upgradin...tioning-guide/

    hope it helps you.. Seems to have a lot of information to help us get the A/C up and running.

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