3406 cat fan work all the time

Discussion in 'Trucks [ Eighteen Wheelers ]' started by yoelmoreira, Jul 14, 2014.

  1. yoelmoreira

    yoelmoreira Bobtail Member

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    Jul 14, 2014
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    hello i buy a freightliner century with a 3406 cat ,1998 and the fan clotch,,is free when the truck have no air ,,,but if i turn on the truck and get air the fan turn on and dont came off again ,,i already change the valve below the antifreeze tank, and still the same ,,please anybody know about ut ,,thank you
     
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  3. rank

    rank Road Train Member

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    Is the manual override switch on?
     
  4. yoelmoreira

    yoelmoreira Bobtail Member

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    Jul 14, 2014
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    no is not swicht on dash
     
  5. tsavory

    tsavory Road Train Member

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    Check temperature sensors one might be bad. Also check the electric wires runs into the air switch.
     
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  6. yoelmoreira

    yoelmoreira Bobtail Member

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    Jul 14, 2014
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    thats the sensor on top of the motor¿.¿ and the wired coming from where¿. bcz i put a new air valve today,, the one below the tank
     
  7. rank

    rank Road Train Member

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    Possibly one of those coolant temperature sensors screwed into the cylinder head is telling the fan to come on. On my 3406 I think it's a two wire switch/sensor located between the two head covers above the exhaust manifold.

    Does the engine fan still come on when the air conditioning is switched off?
     
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  8. yoelmoreira

    yoelmoreira Bobtail Member

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    Jul 14, 2014
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    ok i will tomorrow thank you much
     
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