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spankyjr1, Journeyman
Category: Medium and Heavy Trucks
Satisfied Customers: 2498
Experience:  I worked on all types of equipment semis,forklifts,farm,ect.
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I have 1999 Peterbilt 379. I was going down the road and hit

Customer Question

I have 1999 Peterbilt 379 . I was going down the road and hit a small bump and lost power to motor and gauges . When I try to start the truck , I turn the key and have no power to the volt gauge , heater fan , starter button. I do have lights , power to the starter motor and 1 side of the solenoid on the firewall. The relay behind the gauge panel has power to the large white wires . Any thoughts ?
Submitted: 11 days ago.
Category: Medium and Heavy Trucks
Expert:  spankyjr1 replied 10 days ago.

Good morning Doug sorry for delay do you still need assistance with this?

Let me know I'll be around most of the day

Customer: replied 10 days ago.
still can't figure it out .
Customer: replied 10 days ago.
I'm not sure if the ignition relay is bad or a ground broke .
Expert:  spankyjr1 replied 10 days ago.

Paccar uses a main breaker that feeds accessory circuits through/to the fuse panel ,you need to start there.

The breaker will be either inside frame rail by starter (either side passenger or drivers) or in battery box, you can follow the six gage cable that comes off the positive battery post and goes to breaker, either test both sides for power or jump breaker to test

that breaker has power.

Expert:  spankyjr1 replied 10 days ago.

also test your fuse/breaker panel and make sure both sides and top and bottom have power,, use a volt meter if test light is dim

Customer: replied 10 days ago.
If you are speaking of the 2 - 25 amp fuses by the ECM or starter , they are both fine .
Expert:  spankyjr1 replied 10 days ago.

No those fuses feed engine/trans electronics and go directly to battery positive

you are looking for 2 big breakers, two post, both have larger wires to both sides that feed the entire fuse box

with key on jump that solenoid (outer big post) you talked about in first reply, this may have the accessory solenoid on it

Expert:  spankyjr1 replied 10 days ago.

You also need to know if all fuses have power going through them, (both sides of fuse} even if fuses are okay that will tell us which direction to go either before or after

let me know what you have checked and confirmed

Expert:  spankyjr1 replied 10 days ago.

When you get a chance what engine make and model do you have and is trans electronic (auto shift)?

Customer: replied 10 days ago.
12.7 Detroit 60 series, 13 speed
Customer: replied 10 days ago.
My ignition protection breaker was tripped. Upon resetting it , I have power on both sides but made no difference. I can not find the breakers you sent me a picture of .
Expert:  spankyjr1 replied 10 days ago.

I need to know if entire fuse box has at least 12 v to all breakers/fuses?

Are you referring to ignition breaker in last reply?

Do you know have all gages heater ect in cab with key on?

on the picture of breakers you should only have two inside rame or in battery box

Off battery positive post do you have a 6 gage cable that comes off it?

If you do follow that cable to breaker or solenoid

Expert:  spankyjr1 replied 10 days ago.

click here for engine wiring

click here for breaker I'm referring to, bottom left side of page,, it comes off either battery positive or starter terminal big cable, it feeds all power to fuse panel

Customer: replied 10 days ago.
I have 12 volts to fuse panel , yes I believe that's the ignition breaker ( in harness next to starter ) , no gauges or heater or any type of power when key is on except for lights in gauges and outside. I have 6 gauge wires from batteries but not finding those solenoids.
Customer: replied 10 days ago.
The #6 from my batteries lead to the starter .
Expert:  spankyjr1 replied 10 days ago.

not the battery cables they are either 00/4 or 00/2 cables, the cab power is a little smaller in diameter about the same as car battery cable

so do you have more than one cable to any positive terminal on battery where one is a little smaller than the other cables?

Customer: replied 10 days ago.
I found the problem. The 20 amp breaker at the bottom of the panel has a broke at the terminal.
Thank you for your efforts.
Expert:  spankyjr1 replied 10 days ago.

Here' s the other breaker probably the one you found with broken terminal.

Expert:  spankyjr1 replied 10 days ago.

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