Peterbilt Power Issue

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by snidertrucking4, Jan 6, 2018.

  1. snidertrucking4

    snidertrucking4 Bobtail Member

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    I have a 2002 Peterbilt 379. Truck will start and run with no problem. I have no power to the ACC side of the truck. I have not heat, wipers, power mirror, ect. Anyone have any ideas as to why or where to look. I have checked the fuses under the dash. I am lost and could use some help. Thank you.
     
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  3. GrapeApe

    GrapeApe Road Train Member

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    The Main Accessory Relay in the dash is where I'd start. It's on the left side usually above the fuse panel in the key switch area. It is a large 75 amp relay, part # 16-03405. Key accessory power activates it to power up all the accessory fuses.
     
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  4. ShooterK2

    ShooterK2 Road Train Member

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    First couple of places I'd look are inside the battery box and behind the ignition switch. Look for wires that have come off or disconnected. Any fuses or relays you find should be checked. Also check where the harness plugs into the ECM and the back side of the fuse box.

    I wish I could point you to a more specific place but this is kinda strange that NOTHING is working. Tells me it's gotta be a major wire or a harness plug or something.
     
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  5. ShooterK2

    ShooterK2 Road Train Member

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    Grape Ape knows his business. Check that relay.
     
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  6. Old Man

    Old Man Road Train Member

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    Take out the far left dash panel and the relay is in there, there are 2 in there back to back. Small one closed with the key and energize the big one that power all the acc.

    You can change it, just hard to reach, probably loose a little skin but that is where you problem is
     
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  7. LA runner

    LA runner Light Load Member

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    Super reply.....
     
  8. snidertrucking4

    snidertrucking4 Bobtail Member

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    Ok found the big relay. Used a jumper wire and got everything to work but my cab heater
     
  9. Old Man

    Old Man Road Train Member

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    Hope it is a big wire, keep the fire extinguisher handy
     
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  10. snidertrucking4

    snidertrucking4 Bobtail Member

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    Yes it was a big wire just used it to test the relay. Got the new relay in and everything seems to work
     
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  11. Old Man

    Old Man Road Train Member

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    How much skin did you scrape off?
     
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