C15 engine fan won't shut off

Discussion in 'Trucks [ Eighteen Wheelers ]' started by rollin coal, Aug 31, 2011.

  1. Rigrat

    Rigrat Bobtail Member

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    Nov 21, 2019
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    I have a 04 W900l and I can’t get the fan to go off
     
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  3. RustyBolt

    RustyBolt Road Train Member

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    Considering the fact that the fellow your asking hasn't been on here since 2013, you may want to ask in a new thread. And give as much detail as possible.
     
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  5. jashansuperb

    jashansuperb Bobtail Member

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    Jun 27, 2021
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    Hey I just recharged my ac system yesterday and the gauge was still reading low. The stores had closed by then so I said I’ll do the rest some other time now today at work my fan won’t turn off so I took out the ac relay fuse now the engine fan is working correctly. Any thoughts on what’s wrong how to fix this
     
  6. skallagrime

    skallagrime Road Train Member

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    Your ac high side fan switch is either reading high enough pressure to keep it on or stuck in that position
     
  7. jashansuperb

    jashansuperb Bobtail Member

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    Jun 27, 2021
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    Is that a sensor that needs to be changed where can I find that specifically I have a 2006 KW T800 with a C15
     
  8. skallagrime

    skallagrime Road Train Member

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    Should be a binary or trinary switch that just unscrews. No promises, it OUGHT to be unscrewable without losing your ac charge but as said before, no promises

    Drivers side near top of radiator, kind on the side of the radiator. Just trace the line. Couple of sensor looking things on the line coming outta the condenser coil before the receiver/drier

    Cat wont know anything if you need a part number thats oem stuff, call kw with the last 6 of your vin
     
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  9. jashansuperb

    jashansuperb Bobtail Member

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    Jun 27, 2021
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    It never did this prior to the recharge could it be possible that I may have simply over charged it and my gauge was just reading wrong I put about 2.5 cans of R12

    Drivers side near top of radiator, kind on the side of the radiator. Just trace the line. Couple of sensor looking things on the line coming outta the condenser coil before the receiver/drier

    Cat wont know anything if you need a part number thats oem stuff, call kw with the last 6 of your vin[/QUOTE]
     
  10. jashansuperb

    jashansuperb Bobtail Member

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    Jun 27, 2021
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    What I’m having a hard time understanding is how recharging the ac has anything to do with the engine fan
     
  11. Ridgeline

    Ridgeline Road Train Member

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    It is controlled by the ecm, it is setup to see if the high side of the ac is too high if the fan needs to be running.

    That said if you are putting in R12, you have others issues to deal with.
     
  12. skallagrime

    skallagrime Road Train Member

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    R 12 or r134a?

    Also if youve got a sleeper 2.5 cans is basically nothing, its closer to the 4 lbs mark (6 cans from empty)
    Did you vac and charge or did you just add cans assuming it was low?

    Im assuming you dont know much about ac systems, recommend running through a loves or ta and just paying their price on a vac and charge

    Added:
    Fan reason: because im a glutton for punishment

    Your fan kicks on keeping the refrigerant cooler (and therefore at a lower pressure) on the high side before forcing a too high pressure fault (turns compressor off) or hose rupture.

    The ac compressor will refuse to kick on if it the binary switch sees high side pressure too high (400ish) or low (30ish)

    The fan switch will cycle on around 340ish and bring it down near 200 psi.

    On newer models this may be controlled via ecm but im fairly sure this is essentially a second manual fan switch overide in that model truck.
     
    Last edited: Jun 27, 2021
  13. jashansuperb

    jashansuperb Bobtail Member

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    Jun 27, 2021
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    Yes I had just added the cans I didn’t vacuum anything. So basically there is not enough in there which is causing this correct ?
     
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