1998 378 Engine fan

Discussion in 'Peterbilt Forum' started by NebraskaGMC, Jun 18, 2024.

  1. NebraskaGMC

    NebraskaGMC Bobtail Member

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    Jun 9, 2019
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    N14 Celect+ engine fan will come on with AC pressure and with the switch in the cab, but not with engine temperature. Essentially what that's telling me is I either have a bad ECM, or the ECM controls the fan solenoid with a different relay and I have a problem with either that or the circuit to it. I'm having trouble finding a wiring diagram that incorporates the ac, manual switch, and engine ECM into the circuit, only one or the other. When the fan kicks on either with ac or with the switch I can hear a relay clicking under the dash, but I want to check all the circuits for it before I condemn the ECM because I highly doubt it's that. Anyone have a lead on a proper wiring diagram? I tried the ones in the pinned post and just can't find what I'm looking for. Should be exact same as 379
     
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  3. J.R.

    J.R. Light Load Member

    53
    143
    May 17, 2012
    WI
    0
    Check your fuse box, number 3 spare or 7 spare controls that.
     
  4. NebraskaGMC

    NebraskaGMC Bobtail Member

    22
    12
    Jun 9, 2019
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    If that fuse is blown will the fan switch and the AC still turn the fan on?
     
  5. J.R.

    J.R. Light Load Member

    53
    143
    May 17, 2012
    WI
    0
    Yes, I pulled a few spare marked one's thinking they were spares and caused that problem. Dave from 3 D's Missoula knew it from way back when. They are not marked. Pete used different spares for different functions with different engine's
     
    NebraskaGMC, Deere hunter and Oxbow Thank this.
  6. NebraskaGMC

    NebraskaGMC Bobtail Member

    22
    12
    Jun 9, 2019
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    Going to the farm in a little bit to try that. I'll let you know if it works, thank you
     
    Oxbow and J.R. Thank this.
  7. NebraskaGMC

    NebraskaGMC Bobtail Member

    22
    12
    Jun 9, 2019
    0
    Well I'll be ######. That actually fixed it. Fan works on its own now thank you
     
    Oxbow and J.R. Thank this.
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