Radiator fan randomly going on

Discussion in 'Ask An Owner Operator' started by GYPSY65, Apr 9, 2025.

  1. GYPSY65

    GYPSY65 Road Train Member

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    2019 Pete 579 Paccar mx13

    fan will randomly go on while driving and stay on for 15-20 minutes or so. Then off for maybe an hour or ??

    not running hot or pulling hard. Actually does it flatland and empty

    any thoughts?
     
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  2. Ridgeline

    Ridgeline Road Train Member

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    Is your a/c on or are you using your defroster?
     
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  3. Concorde

    Concorde Road Train Member

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    Fan solenoid is failing and eventually your fan will just stay on.
    When I did mine it was relatively cheap and easy to do yourself.
     
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  4. Magoo1968

    Magoo1968 Road Train Member

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    On my freightliner the Parksmart system causes it to go on. If I leave heat on low fan speed max heat it doesn’t cause the fan to randomly come on for no reason. In summer it’s never a issue only winter/springtime for some reason.
     
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  5. Long FLD

    Long FLD Road Train Member

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    Possibly intake air temp sensor too.
     
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  6. Goodysnap

    Goodysnap Road Train Member

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    Wiggle and pull test the wiring at the fan solenoid on the firewall driver side. Pins can get spread and copper can also break inside the insulation.

    I agree sometimes replacing the solenoid and just repinning the connector would be a good place to start.
     
    GYPSY65 Thanks this.
  7. Arctic_fox

    Arctic_fox Experienced mx13 execrator

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    @Goodysnap beat me to it. That gods #### solenoid is crap and the connector is worse. I had 3 go out on my 579 and it usually took the air temp sensor with it. Id start there and just have the connector replaced. It costs more but the repins never lasted more then a month or two before it went back in when they failed.
     
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  8. RunningAces

    RunningAces Road Train Member

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    If you turn your AC on and the radiator fan comes on what does it mean?
     
  9. Goodysnap

    Goodysnap Road Train Member

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    It means the high side AC pressure has met conditions for cooling needed across the condenser and is part of normal AC operation.
     
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  10. GYPSY65

    GYPSY65 Road Train Member

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    neither
    Sorry. I was off and forgot to check in