Turn signal

citibori · Dec 7, 2012

I have an 07 Peterbilt 379. When I turn the left turn signal on the right and left start to blink but only on the rear of the tractor not anywhere else. It does this for a couple of minutes then my fuse blows. The front lights don't do it and neither does the trailer lights. Only the lights at the rear of the tractor.

Sent from my iPhone using Tapatalk

paullud · Dec 7, 2012

I would check the wires over well that lead to the rear, it sounds like something has rubbed through.

Sent from my ADR6400L using EO Forums

zorry · Dec 7, 2012

As always check the ground.
It's probably a dual filament bulb, like an 1157. Pull bulb out and inspect. A filament will break and touch the other filament. This creates a very easy to repair short. Just change the bad bulb.

citibori · Dec 7, 2012

I disconnected the lights in the back and disconnected my pigtail and still the fuse blows. Is there a flasher for the right and one for the left?

Sent from my iPhone using Tapatalk

zorry · Dec 7, 2012

You'll have to trace the wires foward to find short. The current is coming from dash and is shorting before it goes into the lights.

zorry · Dec 7, 2012

Does the pigtail unplug from trl and the truck ?
If still hooked to truck, I might unhook the wires from the beginning to the pigtail( maybe on the firewall ?) as a broken wire in the pigtail is a common issue,as could be a wire came loose IN the trl plug.

citibori · Dec 9, 2012

If the short was in the pigtail wouldn't it blow the right and left side fuses?

Sent from my iPhone using Tapatalk

zorry · Dec 9, 2012

Well, it would probably affect the trl. If you disconnected the taillights doesyour problem show up ? How do you know ?
So how do you know it isn't in the tail-lights if they're disconnected ?
Does it only happen hooked to a trl ?
If so, when the trl is empty/ light loads or all loads ?

citibori · Dec 10, 2012

No it happens with the trailer disconnected and the two tail lights disconnected.

Sent from my iPhone using Tapatalk

zorry · Dec 10, 2012

Unless someone has a better idea.
1) hook everything up as normal.
Make two little jumper wires to run from a good ground, one to each light. This may require knocking a little paint of a bolt to get to bare metal. Hopefully once grounded well your problem will be gone.
2) start tracing wires. Look for chafing.
Good luck.

paullud · Dec 10, 2012

The old school method would be to replace the fuse with something that won't blow and see where the smoke starts coming from.

Sent from my ADR6400L using EO Forums

Ragman · Dec 10, 2012

paullud said:
The old school method would be to replace the fuse with something that won't blow and see where the smoke starts coming from.

Sent from my ADR6400L using EO Forums

Mdbtyhtr · Dec 10, 2012

Ah the smoke test! If you jumper the offending circuit to a DC breaker, you can trip the breaker quickly when you find the issue.

citibori · Dec 10, 2012

I thought of using the old school method but the fuse that it calls for is a 25 amp and the next one up is a 30 amp. Anyone know of a fuse that I can stick in there that won't blow?

paullud · Dec 10, 2012

citibori said:
I thought of using the old school method but the fuse that it calls for is a 25 amp and the next one up is a 30 amp. Anyone know of a fuse that I can stick in there that won't blow?

You can use a piece of anything that conducts electricity. As stated by Mdbtyhtr you can use a piece of wire with a switch or use 2 pieces of wire that you can quickly pull apart. I would recommend having an extra set of hands and eyes to help watch for the smoke or disconnect the circuit or maybe hold a fire extinguisher so your truck doesn't look like the picture Ragman posted.

Sent from my ADR6400L using EO Forums

citibori · Dec 10, 2012

So I can stick a wire where the fuse goes and ground it? I will have another pair of hands.

Sent from my iPhone using Tapatalk

billg27 · Dec 10, 2012

Don't ground it. Just put the wire or paper clip where the fuse came out.

citibori · Dec 10, 2012

Ok thanks gonna try that tomorrow.

Sent from my iPhone using Tapatalk

Mdbtyhtr · Dec 10, 2012

You are just using a circuit breaker in place of the fuse, instead of a fuse blowing, the circuit breaker trips. You can also trip it manually if you see/smell the wires burning. Then you have found the problem, which is a hot wire on the turn signal circuit which is finding ground or earth for our British folks!

zorry · Dec 10, 2012

This thread is going in a bad direction.
Think it's time to go to a shop.
The advice being given to someone with little experience in these things I'm afraid may put him in worse shape.
If things go bad, he'll be in the shop for a major repair.
Go to a shop while it's a minor repair.