1998 Kenworth t800 fan runs constantly

Discussion in 'Kenworth Forum' started by breynolds, Sep 3, 2025.

  1. Sep 3, 2025 #1
    breynolds

    breynolds Bobtail Member

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    I have 98 t800 an previous owner removed ac system I believe this to be my problem but don’t know where to begin as the only 2 wires that may have been pressure switch (green an brown) don’t make a difference if I jump them. So ever since I have bought truck the engine fan runs constantly it’s a c10 so already lacking power from the start.
     
    breynolds, Sep 3, 2025
    breynolds, Sep 3, 2025
    #1
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  3. Sep 4, 2025 #2
    Lazer

    Lazer Road Train Member

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    When you say ‘removed the ac system’ what all was removed? Just the ac compressor? Wiring in the loom? Evaporator coil?
     
    Lazer, Sep 4, 2025
    Lazer, Sep 4, 2025
    #2
  4. Sep 4, 2025 #3
    Star Rider

    Star Rider Road Train Member

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    How long did you jump the wires for?
    The default time for CAT is 180 seconds.
    You have to leave it jumped for 3 minutes for the fan to disengage.
     
    Star Rider, Sep 4, 2025
    Star Rider, Sep 4, 2025
    #3
  5. Sep 5, 2025 #4
    Lazer

    Lazer Road Train Member

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    It is possible the ‘fan clutch’ is seized. If that is the case, all the checking and trying this and that will not help, the fan clutch will need to be replaced.
     
    Lazer, Sep 5, 2025
    Lazer, Sep 5, 2025
    #4
  7. Sep 5, 2025 #5
    breynolds

    breynolds Bobtail Member

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    Oh ok thanks I do not think I tried long enough I will try that again
     
    breynolds, Sep 5, 2025
    breynolds, Sep 5, 2025
    #5
  8. Sep 5, 2025 #6
    breynolds

    breynolds Bobtail Member

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    Sep 3, 2025
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    Compressor was removed, wiring still there but any plug or connector or for example pressure switch looks like wires were just cut off at it
     
    breynolds, Sep 5, 2025
    breynolds, Sep 5, 2025
    #6
  9. Sep 6, 2025 #7
    breynolds

    breynolds Bobtail Member

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    Sep 3, 2025
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    Left jumped today at start up an seems to be working as should now thank you
     
    breynolds, Sep 6, 2025
    breynolds, Sep 6, 2025
    #7
    Star Rider Thanks this.
  10. Sep 6, 2025 #8
    Star Rider

    Star Rider Road Train Member

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    You can make sure those are the high pressure sensor wires by un-jumping them while the motor is running, fan should kick on.
    Jump them again while motor is still running and the fan should kick off after 3 minutes.
     
    Star Rider, Sep 6, 2025
    Star Rider, Sep 6, 2025
    #8
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