KW w/ ISX engine fan issues

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by devedo, Jul 22, 2021.

  1. devedo

    devedo Light Load Member

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    Aug 11, 2015
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    Needing some insight. 2010 Kenworth T8 1XKDD49X8AJ262684 with Cummins ISX 79360158 with an engine fan that's constantly running when parameters are set like they should be.

    AC input switch and coolant temp sensor are reading correctly. Fan control status states that engine fan is on due to fan control switch or data link control. Fan switch is off and even with fan override switch disabled...still reads the same. If the parameters for on/off voltage is flipped the fan stays off constantly and fan override switch does not engage fan.

    Fan switches have been swapped. Test ecm was tried. Fan override was also disabled with the test ecm and still read the same fan status. Manually powering the fan solenoid with a probe works as it should kicking on and off.
     
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  3. MLC Adventures

    MLC Adventures Medium Load Member

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    What are the exhaust, oil, and coolant temps reading?
     
  4. Inderjit

    Inderjit Light Load Member

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    I had a 2007 KW in the shop for a fan running continuously.
    It had a temp sensor for the fan in the power steering reservoir.
    There was a broken wire going to that sensor.
     
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  5. baha

    baha Road Train Member

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    Also ck. the eng. temp. sensor on the eng. that now has more wires leading every/where and you will have to ck. all of them to see if there is a raw place in a wire where they have been rubbing together or on a clamp that had rubber on them when new but after a few years the rubber goes away and rubs all the wires that are held raw and short out and make things diff. to find the exact place that wiring harness is worn thru, I have found replacing the Eng. temp. sensor fixes some trucks with fans running all the time, the intake, A/C, eng. temp. and about 4 other sensors will turn on fan ?
     
    Last edited: Jul 22, 2021
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  6. Dave_in_AZ

    Dave_in_AZ Road Train Member

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    Yea there's like 8 or 9 sensors that will do the fan.

    On mine is was the low side AC switch that would go bad.

    The AC has 3 all by itself lol.

    Unplug them all one at a time and put a jumper wire in the lead.

    All those sensors are normally closed.

    When you put the jumper in one, and the fan de-clutches, you have your culprit.
     
  7. devedo

    devedo Light Load Member

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    ECT 108. EOT 107. EGT 111. FUEL 105
     
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  8. north60

    north60 Bobtail Member

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    hook up a manifold to the AC system and check for high pressures. Had a sticking TXV cause that a while back. Intermittently spikes in pressure causing the fan switch to turn the fan on. It is usually on for a minute before it turns off. but if it keeps spiking in pressure it will keep turning it on before the minute passes.
     
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