T600 AC issue, clutch not engaged, then suddenly works.

Discussion in 'Kenworth Forum' started by Patriotleasing, Aug 30, 2021.

  1. Patriotleasing

    Patriotleasing Bobtail Member

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    Jan 1, 2017
    0
    AC was working fine, stopped at rest area, came out AC blowing warm. Checked under hood, AC clutch NOT engaged. Changed relay, nothing. Started driving, 5 minutes later, blowing cold. Blew cold for 30 minutes, pulled into my yard, dropped my trailer, climbed back into cab, guess what? No AC again. Open hood, clutch not spinning again. Soon as I started bob tailing home...yup, blowing cold again. I hate AC gremlins. Any idea? Any help would be greatly appreciated. Kinda hot down here in good ole FLA!
     
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  3. 1985mudflap

    1985mudflap Bobtail Member

    18
    5
    Aug 30, 2021
    0
    I'm having similar problems with my 99 w900. Is your engine fan coming on automatically?
     
  4. MM71

    MM71 Medium Load Member

    646
    703
    Jun 28, 2008
    AZ
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    Check wire and connector at pump for a break. They vibrate and tend to break. Otherwise, either purchase a new relay or swap the relay in the fuse box.
     
  5. Ross_Tech

    Ross_Tech Light Load Member

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    111
    Aug 31, 2021
    Michigan
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    It sounds like the fan isn't coming on when its supposed to, or the condenser fins have debris, that is reducing it's ability to condense while stationary. You should be able to unplug the fan solenoid to get the fan to run continuously and see if it cools down while sitting.
     
  6. Patriotleasing

    Patriotleasing Bobtail Member

    22
    3
    Jan 1, 2017
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    Turned on the fan manually to no avail. AC clutch still refused to engage. Thanks.
     
  7. skallagrime

    skallagrime Road Train Member

    1,790
    3,665
    Apr 10, 2012
    Indiana
    0
    Only for troubleshooting:

    Supply ac clutch with known good 12v, verify it isnt flaky

    Check ac box when its on but not blowing cold, is there reduced airflow or is it just as strong but compressor refuses to cycle on? Low air flow indicates freeze switch is shutting ac off, but getting "stuck" in the off position here and there

    Verify operating refrigerant pressures, could be a blockage on the high side or at the expansion valve which would read far too low on low, far too high on high side resulting in ac clutch turning off till enough high pressure is bled through the exp valve
     
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