engine fan

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Superhauler, Jul 1, 2013.

  1. Superhauler

    Superhauler TEACHER OF MEN

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    ok, my engine fan wont turn off today. it isn't the a/c pressure switches or the manual switch that is bad. the control valve/pressure switch on firewall was installed a few months back. what am I missing? I pulled a wire off the valve on firewall and the fan turned off. but I think I just killed the power from the wire when I did that.
     
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  3. GrapeApe

    GrapeApe Road Train Member

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    If you unplugged it and the fan quit, then the solenoid, air and fan clutch are working OK, it's electrical. Does your ECM control the fan, or do you have a separate switch? There's a quite a few ways that manufacturers control the fan.
     
  4. Superhauler

    Superhauler TEACHER OF MEN

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    yeah fan hub is ok. it is electrical either ecm is acting up or like you said the solenoid has gone bad already. I have my old one in the bunk think i'll hook it up and see what happens.
     
  5. GrapeApe

    GrapeApe Road Train Member

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    I don't think it's the solenoid, if the fan shuts off when you unplug it and turns back on when you plug it in, then the solenoid is working. You can double check it by unplugging it and giving it power & ground. You should be able to release & engage the fan. What I'd do, if you have the option, is to hook it up to a laptop and watch the fan output to see if the ECM is commanding the fan on. If it's not, then your problem is on the fan solenoid wiring side. If the ECM is turning the fan on when it's not supposed to, then you have to figure out why. It could be a bad temp sensor, not totally failed to set a code, but reading high enough to turn on the fan. Tough to diagnose without a computer though.
     
  6. Superhauler

    Superhauler TEACHER OF MEN

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    found the problem, the a/c high pressure switch is gummed up with oil. had a line break last summer and fixed it in a truckstop parking lot. filled with those cans of Freon off the shelf that have the oil in with the Freon. basically I have to much oil in the system. took the switch off and left it hang and after a while the fan started working like it should. put the switch back on and after a few cycles it would start to act up again.
     
  7. GrapeApe

    GrapeApe Road Train Member

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    A/C would have been my first guess, but you said that wasn't the problem:biggrin_25512: Glad that you found it though, those kinds of problems can be very tough to find.
     
    superhauler Thanks this.
  8. Superhauler

    Superhauler TEACHER OF MEN

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    update, just found the problem after installing a new pressure switch. it still was acting up. got to looking and did a (pull test) on the short wire harness that runs from pressure switches to about 18 inches back to another plug. had a wire that had pulled apart in the sleeve. spliced it and all is well now. new wire harness tomorrow and all will be good in the world again!:biggrin_25520:
     
    silver dollar Thanks this.
  9. silver dollar

    silver dollar Medium Load Member

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    Thanks for posting you results. I'm having a similar problem. I'll start looking at what you did, on mine.
     
  10. little cat 500

    little cat 500 Road Train Member

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    i had a problem like that for a couple weeks this week the fan an the front of the hub went though rad
     
  11. silver dollar

    silver dollar Medium Load Member

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    WOW!!!!!!!
     
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