fan coming on

Discussion in 'Trucks [ Eighteen Wheelers ]' started by heavyhaulerss, Aug 16, 2013.

  1. heavyhaulerss

    heavyhaulerss Road Train Member

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    My fan comes on as if I were running my a/c. but I have no a/c. no a/c condenser, no belt on compressor. I remember when my a/c was working, the engine fan would kick on from 1st thru about 3rd or 4th gear & then shut off. it is doing that now? pulling a grade fan comes on for a minute or less then off. after driving a hundred miles, I can shut truck off for 2 hours when starting back up water temp is 150-170 & as soon as engine is running fan comes on for 30 seconds or until I hit 3rd-4th gear if moving. I remember replacing a switch on my a/c compressor 14 years ago. could it be bad? I thought some one told me when the head builds up too much pressure the fan will kick on.
     
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  3. dude6710

    dude6710 Road Train Member

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    You have it on defrost?
     
  4. magoo68

    magoo68 Road Train Member

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    maybe intake air is hot so it comes on to cool charge air until airflow is high enough to do it on is own?
     
  5. heavyhaulerss

    heavyhaulerss Road Train Member

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    o.k. never thought of this, but fan never came on like this before, except when a/c on. like I say. it cycles just as if the a/c was on. it is not a big deal. I don't see it hurting anything. just trying to figure it out.
     
  6. heavyhaulerss

    heavyhaulerss Road Train Member

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    it is not on defrtost
     
  7. magoo68

    magoo68 Road Train Member

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    another possibility is a minor air leak to fan hub that takes a few minutes to disengage clutch
     
    heavyhaulerss Thanks this.
  8. Heavyd

    Heavyd Road Train Member

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    Sounds like the engine is seeing high intake air temp, or high boost temps.
     
  9. heavyhaulerss

    heavyhaulerss Road Train Member

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    o.k. no codes. what would cause the engine see high intake temp or high boost? I have no boost gauge. could it be a leak in the air to air? or one of the hoses ?
     
  10. claytonr1973

    claytonr1973 Light Load Member

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    Not having a belt on the compressor won't keep it from coming on. The clutch is energized by the same wire that tells the fan to come on if pressures warrant it. If your defrost is on or you have it on a/c with the blower running it will tell the fan to come on. It could also be a the pressure switch. You need to see if any codes are being set.
     
  11. Heavyd

    Heavyd Road Train Member

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    Bad sensor or wiring could be causing it. Really only way to see what is going on is to have a laptop connected to it and see what inputs are triggering the fan, if any. I'm not sure of the threshold between what temp the ECM reads to turn on the fan vs set a code for high intake temps. Usually the ECM's are programmed to protect the engine and will derate the power when temps are too high. What engine do you have?
     
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