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No Brake lights (edited title)

ak diesel driver

ak diesel driver

6.5 driver
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alaska
So the other day the smoke was let out of this little red/white wire 18-20 gauge. At least that was the only thing I could find that had been hot. It goes up to the key switch along with 2-3 others. So along with this my brake lights have been acting up. I currently have none. It's blown both the stop/hazard fuse and the brake fuse. Both are good now. I cut and jumpered the wire temporarily but still nothing. I've searched my FSM and can't find anything that shows that wire at least not in anything related to brakes. Any help would be appreciated.IMG_20180525_202528.jpg IMG_20180525_202612.jpg
 
So I figured out why my brake lights weren't working. Changed the brake switch and it started working but seemed to flicker at first. Then put everything back together and went to back out and couldn't get it out of park. Then it started smoking again. Blew the brake fuse so I replaced it and started trying to find it , I finally reached in to wiggle the brake switch connector and saw a spark. Got to feeling the wires better and the insulation on the wires is fried. So enough fun for tonight I guess tomorrow afternoon I'll get to rip apart the dash enough to see in there and fix the wires.
 
Have fun, I hate auto electrical. I did a complete re wire of my 1977 GMC grain truck last winter.:(
 
Example # 324 that smoke is good for wires. Seems you let the smoke out, and now it’s no good.

Are you sure it wasn’t so cold the truck just decided to try heating it’s self up?

Sux man. Sorry for the annoyance. Not me being annoying- I mean the problem- that’s just how I am.
 
I am asking this. Is this just the fuse? Is there another problem that caused the high current? Or was there a chafe that shorted and snowballed in this harness section?
 
No way a bad fuse could cause this. Bad ground and one circuit feeding another is theoretically possible but crazy rare.

My $ is on a chafed wire. It probably barely made a connection to ground and popped the fuse that started his search. When he wiggled them it made a better short to ground than it had before.
The original fuse was old and from age/ vibration blew nice and easy but the new one held its load long enough to let the wires get hot and melt down.

The other option is that a couple of positive circuits wore the insulation out between them, a small wire and a larger one. Then when the load of the larger one came onto the small wire from the wiggle giving better connection it pulled more of a load then the small wire could supply, overheating it electrically, then thermally.

Either way the new lil harness is needed and upon install careful check of the load on the affected circuits to ensure no repeat.

Hook in the new harness with fuses removed and test for circuit shorts. Starting out with a couple tiny amp fuses might be in order as well. Better to pop a couple fuses in testing than more wire.

Was there any signs of rubbing where the harness fit that you suspect?

You swap any tail lights or anything in the circuit recently? Tow a different trailer?
 
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No it's not the fuse or chafing of that small harness. The 2 wires that get hot are the orange and white ones. The orange is power in from the stop/hazard fuse the white becomes hot when you step on the brake. The white wire splits into 5 different feeds one to the multi function stalk, one goes to the brake relay and then the multi function stalk, one goes to the ecm I believe for TCC, one IIRC goes to the ABS, and one I haven't identified.
Those 2 wires obviously are acting like a fusible link. I'm thinking of splicing a fuse into it just to protect that little harness until I get this figured out.
It's got to be one of those 5 sources shorting it out
 
Worst part is that I could have more than one issue now that things have gotten hot a couple of times, ie wires melting together in a harness somewhere.
 
What about removing 12v battery that is over maxing the bad circuitry. Connect a 9v battery like a smoke detector uses and chase the circuit hot. That shouldn’t have enough amps to get anything hot but still ID an issue.
 
I guess you'll have to explain that a little better my friend. If it doesn't get hot how do I know there's an issue? I was thinking that if I installed that smaller fuse if it didn't pop I'd know I found the issue.
 
Yeah, that's what I was meaning to ask. If this section sorta became a fuseable link type wire. I was questioning just replacing the section might repeat the problem.
 
Learning as you are posting and thinking about it. I would think it might be good to try and remove all split off circuits and add them back one at a time. Maybe unplug lights as close as you can to this node. Take out flashers etc. Add stuff back in one at a time and see if a very small fuse blows just wires then add load probably have to increase fuse incrementally with circuits and loads.
 
One other thing I forgot to mention is when the brake lights don't work everything else seems to work fine. Turns, hazards, TCC,etc.
 
I first noticed my trailer brake controller didn't work a couple of weeks ago so I've probably been driving for awhile with no brake lights and didn't realize it.
 
From what Will said. If it is some shared wiring or node combination. Would it be good to put small fuses in related circuits to see if anything pops just a wiring short.

That sounds like the first thing I would look at the trailer brake controller and plug wiring. When you replaced the hitch I assume you messed with the trailer plug. Something might have come loose in the trucks trailer connector plug.

Once had a similar short in the trailer connector that when I was pressing the brake pedal in reverse a trailer plug wire back fed to a shared node and the truck wouldn't shut off with the key. If I took my foot off the brake pedal or out of reverse (remember I am a manual transmission) the truck shut down with the key like normal.
 
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Schiker has it right on seperate the circuits and add back one at a time.

Testing for grounded circuits with batteries disconnected is the safest way.

The tail Light “pc board” things SUCk and have issues. You can Pull the lights and inspect them real quick and easy.

Possible component failure that comes to mind: brake controller, turn/hazard assembly, ignition switch, trailer connector shorting, tail light assembly.

Using the wires getting hot or fuses blowing as indicator if something is wrong is bad idea. Something is wrong, I promise.

You need a short circuit finding tool for this one. The backyard trick was to keep it powered up and slowly move a magnetic compass over the wires until the needle swings then examine there. Not super successful but it was something. The 2 best ones I have used I will post below after some searching for one online pic, other in my garage.
You have my number if I can help that way too...
 
Definitely a short to ground some place in the system. Tough to see every piece of wire where they cross over a bare piece of steel.
I hope You find it without too much trouble.
 
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