AC not working, electrical

Discussion in 'Peterbilt Forum' started by kwforage, May 13, 2018.

  1. kwforage

    kwforage Road Train Member

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    Jun 3, 2007
    Wisconsin
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    2005 379. Compressor clutch doesn’t kick on. Has freon. High and low pressure switches show closed, also jumped with a paperclip and nothing. Put a test light on high or low pressure connector when unplugged and the clutch engages. This led me to find I am not getting a ground to the AC relay in the fuse panel. If I manually ground the relay the clutch engages. I am assuming the high and low pressure switches create a ground for the relay when closed? Is there something else on that circuit I’m missing? Any other ideas?
     
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  3. KwT800c15

    KwT800c15 Bobtail Member

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    May 16, 2018
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    Iam having the same problem too. Did you find out what the problem es a?
     
  4. kwforage

    kwforage Road Train Member

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    No, if I do I’ll let you know
     
  5. Expeditor

    Expeditor Medium Load Member

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    Did you jump the pressure switches or did you put one leg of light on ground/hot and the other to the switch?
    Usually if you jump the pressure switches and the compressor starts that would mean you have a bad pressure switch or low on gas.
     
  6. Loaderlou

    Loaderlou Medium Load Member

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    Feb 24, 2014
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    Hi Kw. Check your fuses for oxidation on the spades. Aluminum tends to oxidize over time and you will loose connection. I had lost a few gauges recently and s friend suggested changing the fuses. Put all new ones in and everything worked again. Also just recently changed my evaporater, looked like a birthday cake. 03 pete.
     
    Justrucking2 Thanks this.
  7. nasriza

    nasriza Road Train Member

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    so the ground on the relay from what i see in the diagrams comes straight from hvac control it goes thru both high and low psi switch goes to the bunk blower relay and then to the hvac relay, it might also be dash switch. chase the ground and see where its missing.
     
  8. kwforage

    kwforage Road Train Member

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    So ground comes from the AC switch on the dash?
     
  9. nasriza

    nasriza Road Train Member

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    it does not come from there it goes thru there. and then ac compressor has constant ground and it gets power as request to turn on and off.
     
    kwforage Thanks this.
  10. kwforage

    kwforage Road Train Member

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    It was the AC switch in the dash. It was dirty inside the the contacts weren’t working. All good now!!!
     
  11. nasriza

    nasriza Road Train Member

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    Chicago, IL
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    well you got it figured out.
     
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