2001 peterbilt 379 Detroit 12.7 60 series fan won't stop running.

Discussion in 'Peterbilt Forum' started by Tylers1220, Apr 29, 2024.

  1. Tylers1220

    Tylers1220 Bobtail Member

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    First time poster on this site and want to just say thank you in advance for the help. I have a 2001 peterbilt 379 with a 12.7 detroit series 60 and the engine fan will not stop running. I checked the solenoid it has 12 volts I changed the 2 prong sensor that goes from head to ecm. Checked all fuses except for the ones behind the switch panel in the dash because I can't find anywhere that says what they are. I have good air going to the solenoid and air out. Also this all started when my engine temp gauge started to not work. It stays under 100 until I shut the truck down and then it goes up to almost 180. Any ideas for what is wrong would be great.
     
    blairandgretchen Thanks this.
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  3. blairandgretchen

    blairandgretchen Road Train Member

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    Passenger side of head I think there’s 3 sensors.

    @sawmill explained it better to me, but I think one is high temperature, one is lower temperature, one to guage?

    Thinking that the high temperature sensor may be bad?

    A ‘scan guage’ is useful with these engines, they’re about $150 - reads the ECM fed data, so you can eliminate or diagnose bad or inaccurate dash guages.

    Any of that make sense?
     
    Big Road Skateboard Thanks this.
  4. Tylers1220

    Tylers1220 Bobtail Member

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    So there is 3 on that side of the head. Far right is the ECM with power and ground the other 2 is what I'm not sure which one is which.....I also put a volt meter on those and there only getting around 4 volts. Should they all be getting 12?
     
    blairandgretchen Thanks this.
  5. blairandgretchen

    blairandgretchen Road Train Member

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    The other two, I think are high and low.

    I’m not sure what voltage or resistance they should measure at.

    @sawmill , @pushbroom @OLDSKOOLERnWV ,

    I’ve got to run to the store, but I’ll grab the shop manual when I get back if someone smarter than me hasn’t chimed in.
     
  6. Tylers1220

    Tylers1220 Bobtail Member

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    Awesome thank you. Also with the key one and the manual fan switch in the on position in the dash I do not have power to the solenoid....is that how they work no power to the solenoid to engage it?
     
    blairandgretchen Thanks this.
  7. blairandgretchen

    blairandgretchen Road Train Member

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    Oooh. Good question.

    Is the default position for the solenoid to be open or closed if switched power failure occurs?
     
  8. Tylers1220

    Tylers1220 Bobtail Member

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    Yes so with the key on but not running and switch off I have 12 volts going to the solenoid and if plug it and unplug it the solenoid releases air. But when the truck is running and the switch on or off it doesn't make a difference I did the same thing and plugged and unplugged and nothing happens. I'm not sure that all made sense and kind of confusing to read.
     
    blairandgretchen Thanks this.
  9. Tylers1220

    Tylers1220 Bobtail Member

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    Yes so that is the sensor that I have already changed. The other sensors are single post. I know one goes to the gauge but I don't know what the other single post sensor does.
     
    blairandgretchen Thanks this.
  10. Big Road Skateboard

    Big Road Skateboard Road Train Member

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    Coolant temp, oil temp, A/C high pressure, manual fan switch.

    That's about all, and associated sensors, that'll make your fan come on with your truck.
    ( I think, pretty sure yours should be all ECM controlled)

    Did it start with A/C use?

    Do you hear your fan solenoid switch when you key on?

    Do you have a pic of the right rear of head and t stat housing?
     
    Last edited: Apr 29, 2024
    blairandgretchen Thanks this.
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