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No power to AC compressor

Discussion in 'Peterbilt Forum' started by zircon, Jul 2, 2011.

  1. Jul 2, 2011 #1
    zircon

    zircon Bobtail Member

    23
    5
    Mar 12, 2010
    Austin Texas
    0
    2000 Peterbilt 379. No power to AC compressor. Power is at switch on dashboard, but can't trace power past switch. What wires from switch take power to the compressor. Pressure switches appear to be closed. What terminals on AC switch are hot when switch is closed? Thanks for any info.
     
    zircon, Jul 2, 2011
    zircon, Jul 2, 2011
    #1
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  3. Jul 4, 2011 #2
    SL3406

    SL3406 Medium Load Member

    550
    1,492
    Jan 10, 2011
    Oklahoma
    0
    Power for the compressor clutch comes from the relay in the fuse panel. The pressure switches are on a ground circuit. You can unplug the wire and jump across with a paper clip to test if the pressure switches are closed.
     
    SL3406, Jul 4, 2011
    SL3406, Jul 4, 2011
    #2
    zircon Thanks this.
  4. Jul 4, 2011 #3
    zircon

    zircon Bobtail Member

    23
    5
    Mar 12, 2010
    Austin Texas
    0
    Thanks, SL3406. Had actually checked that already,and that's not the problem. Thanks for the suggestion though. Appreciate your input. I'll keep working on it.
     
    zircon, Jul 4, 2011
    zircon, Jul 4, 2011
    #3
  5. Dec 1, 2011 #4
    texas rattler

    texas rattler Light Load Member

    76
    13
    Aug 7, 2011
    cat spring texas
    0
    if the relay is good i would look for a thermostatic switch on the evaporator box,typical a/c systems will use this to control compressor.im assuming the pete has one.it has to have some way to signal the comp. as you move the lever from say vent to a/c. good luck
     
    texas rattler, Dec 1, 2011
    texas rattler, Dec 1, 2011
    #4
  7. Oct 24, 2015 #5
    AZ379PETE

    AZ379PETE Bobtail Member

    5
    0
    Oct 24, 2015
    0
    Had same problem it was in my, ignition.
     
    AZ379PETE, Oct 24, 2015
    AZ379PETE, Oct 24, 2015
    #5
  8. Oct 24, 2015 #6
    GrapeApe

    GrapeApe Road Train Member

    2,215
    2,211
    Jan 7, 2013
    0
    http://www.supermiller.com/pdf/sk25762.pdf

    This should a schematic for your 2001. Looks like the A/C clutch is wire 93 that goes right to the relay. All other switches turn the relay on/off, so the first thing I'd do is make sure the relay has power and then jump to top make sure the clutch comes on. If it does, the wiring to the clutch is good. Then you have a bad relay or wiring on the other side of the relay. If it doesn't, you have a problem with the wiring to the clutch.
     
    GrapeApe, Oct 24, 2015
    GrapeApe, Oct 24, 2015
    #6
    QUALITYTRUCK Thanks this.
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