T800 fan running

Discussion in 'Kenworth Forum' started by Kmac111, Oct 23, 2019.

  1. Kmac111

    Kmac111 Bobtail Member

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    Oct 23, 2019
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    I have a 2014 T800 with Cummins ISX and the engine fan stays running all the time now. Insite is saying the a/c pressure switch is turning on the fan. Unplugged and it still runs. Anything else I’m missing?
     
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  3. AModelCat

    AModelCat Road Train Member

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    A/C might have more than 1 switch. Sure you got the right one?



    Not at all familiar with current generation trucks and Cummins on-road engines so this might not apply at all:

    Does Insite show the A/C switch still commanding fan on after unplugging it? Wire might be shorted to power or ground, tricking the ECM into thinking the A/C system needs the fan on?
     
  4. Goodysnap

    Goodysnap Road Train Member

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    Did you jump it to check response? Fan switch is normally closed for engine fan off.
     
    BoxCarKidd and AModelCat Thank this.
  5. Kmac111

    Kmac111 Bobtail Member

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    Oct 23, 2019
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    I’ll check the wires in the morning. It does say the ac is making the fan run while unplugged. Been chasing my tail it feels like.
     
  6. starmac

    starmac Road Train Member

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    I had a wire break right at the plug in for the sensor on my AC compressor, and could not be repaired, I came on up to Alaska in some serious cold temps and had to change the sensor to get my fan to shot off. In hindsight I could have tied the wires together or grounded it to have made it work, but didn't think of it at the time. I do not remember if it was a one wire or two wire sensor.
     
  7. north60

    north60 Bobtail Member

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    if jumping the wires does not work. Likely a broken wire. I replaced the wiring on an ISX from the rear left side of the engine to the a/c switch and ac clutch and coolant level sensor, all wires were damaged from loom along the left side of the engine. THis was on two units one was ISX CM871 and a CM2250.
     
  8. Freddy2times

    Freddy2times Light Load Member

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    Sid fmi? Using insight it should code.
     
  9. ahrenbatrhhllc

    ahrenbatrhhllc Bobtail Member

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    Nov 11, 2020
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    I hate to bump an old thread as my first post, however, I DID use the search function and found this thread. I have a 2013 t800 with a Cummins ISX as well. Fan stays on no matter what. I have checked it with insite and it says that its because of a/c high pressure. Problem is, I evacuated the system so there's no r134 in it. I also first replaced the high pressure switch, then just jumped the plug. Just for fun I also jumped the plug that is in the a/c line coming off of the compressor. Still doesn't shut off.

    I checked for continuity in the wires from the high pressure switch up to the firewall, both of the wires checked out. The fan hub has been replaced and if I put air to it manually, it does disengage so it isn't the hub. I did test for signal going to the high pressure switch with the truck running, but did not get a signal on either wire. This has led me to believe it may be a broken wire in the cab, OR, a bad ecm. However, I don't even know if the ECM controls it or if its the CECU.

    This is more than a nuisance as now it has caused my truck to need a regen and even with using insite to do a "forced" regen, it fails because the truck can't get up to full temp.

    Not related (I think) I also had to recently replace the outlet Nox sensor. Due to running so cool, not getting up above 185 even when hauling, my intake manifold boost pressure sensor was all carboned up as well. I found that when the truck derated and threw a code for no boost pressure. I'm at a loss and the only thing I can think of is testing the fan circuit at the ecm...but I have no idea what pin it is or if its controlled by the CECU or the ECM or what.

    Anyone offer any ideas?
     
  10. Goodysnap

    Goodysnap Road Train Member

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    The engine fan is ECM controlled. Do you have good air supply to the fan control solenoid? Does the fan solenoid function? Are you sure you jumpered the fan switch and not the AC cycle switches? Fan switch should be normally open. Closed or jumpered should change you input signal to Insite(ECM).

    Some things to check. Spread pins or broken wires inside the insulation are somewhat common on either the fan switch or the solenoid both.
     
  11. ahrenbatrhhllc

    ahrenbatrhhllc Bobtail Member

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    The fan solenoid has been replaced, it’s not functioning as the ac switch is activated turning it off essentially.

    I jumped the ac high pressure switch next to the air dryer itself. I will check insite tomorrow with it jumpered and without to see if it changes.

    I will try to find an ecm pin out to check the signal voltage.

    Oh. And I do have good air supply. One of the first tests I did.
     
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