01 T800 engine fan auto on/off? anyone have Schematic? Acting backwards

Discussion in 'Kenworth Forum' started by Green461, Mar 28, 2020.

  1. Green461

    Green461 Light Load Member

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    Southern WI
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    2001 T800 DD 12.7L I noticed awhile ago when I start the truck and let it warm up, before the temp gauge even starts to move my engine fan will sometimes come on, not always, then once warmed up it shuts off. Its also come on a few other times, usually only when idling and its definitely not hot. Actually cooler.

    I changed thermostats year ago, was only warming up to about 150, now it sits at 190-195 like it should, never moves, so its functioning as it should. Except some big hills, only happened a couple times.... Temp started climbing, went up to 215 and was going higher, fan never came on automatically so I hit the manual switch to turn it on, and temp came down to normal.

    Anyone have a schematic for this circuit? What temp switch activates the fan? At what temp?
    There are a few temp sensors in the water jackets, curious to know which one is for what.
     
    Last edited: Mar 28, 2020
  2. spsauerland

    spsauerland Road Train Member

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    By chance, did you have defrost on? Also, need last six of VIN for diagrams.
     
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  3. Green461

    Green461 Light Load Member

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    Yes, im sure i had it on, I leave it on a lot... I see the AC circuit turns it on now... Im curious at what temp it should automatically turn on?
    Last 6 of vin - 869782
    Thanks.
     
  4. spsauerland

    spsauerland Road Train Member

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    Looking up your S/N, your truck has a DDECIV 430/500 from factory. The fan is controlled by the ECM. The ECM controls the low side (ground) of the engine fan relay to cycle the fan as needed. The coolant gauge reading and high temp warning light are signaled from Kenworth supplied sending units, not the engine ECM. You would have to verify with DDDL, but most I seen with DDEC fan controls turn fan on around 210 F and remains on for 180 seconds. Here is description of fan control from Detroit manual,
    The DDEC IV ECM continuously monitors and compares the coolant, oil, and air temperature,


    engine torque, engine operation mode, and various optional inputs to calibrated levels stored

    within the ECM. These limits are factory configured based on application.

    When these temperature levels exceed the preset fan ON temperature value, the ECM will enable

    the fan control digital output(s) that activate the fan. The fan will remain on, cooling the engine

    with the increased air flow until the temperature levels reach the preset fan OFF temperature.

    At this point, the ECM will switch fan control to battery ground, which will deactivate the fan,

    effectively maintaining the coolant temperature between the two preset levels.

    I attached the DDEC wiring diagram and engine harness layout for you. It says DDECIII, but all four diagrams were for the updated power distribution box after 12/01 builds.
     

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  5. Green461

    Green461 Light Load Member

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    So my gauge working correctly would be a different temp sender than the ECM reads.... hmm. I will see what the wires and everything looks like. Thanks.
     
  6. QUALITYTRUCK

    QUALITYTRUCK Road Train Member

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    romulus,mi
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    Both sensors located on rear passenger side of cylinder head. Larger one is for ECM.
     
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