Electrical short causing brake lines turn red hot and starting fire

g.hayduke said:
With mountains of respect to @mrblaine , the only way I see a winch grounding problem as the culprit is if the winch is somehow grounded to the brake lines instead of the battery. Seems unlikely but obviously possible. And I think that problem would only show up while winching which was not the scenario described by the OP. Winch would have current flow through it only while operating.
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Here is what I know but need to verify the minutia of. I have several instances of brake customers and friends relating that they have smoked the brake lines red hot while hooking up their winches. Something to do with which order the cables are hooked up and what the end of the cable not being hooked up was laying against.
 
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Jerry Bransford said:
If you understood what happens if a winch isn't grounded directly to the battery you wouldn't think that.

First, a winch can draw over 400 amps when loaded. If both of the winch's power cables are connected directly to the battery life is good... the winch doesn't need to use any of the wiring anywhere in the Jeep. But if the winch's negative lead is connected to the chassis instead of the battery, the winch will pull that 400+ amps through the Jeep's ground connections between the chassis and the battery. The problem is even in total those factory ground connections are not anywhere close to being able to conduct the amperes a winch can draw which will start them glowing red then popping.

The term for the above is 'scavenging' aka 'ground scavenging'

In other words if a winch's main ground lead is not properly connected directly to the battery's negative post it can and will start blowing any connections it finds between the chassis and battery.
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We had a large 2/0 negative on an ambulance 250 amp alternator break off while it was running. The amount of switches, relays, and everything that could be back fed and killed was astounding.
 
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g.hayduke said:
That's why I suspect it's a short to ground, probably directly to the brake lines or a braking component.
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Yes, it does seem it would have to be a short directly to a brake line. A short to metal (ground) would have no reason to go through the brake line to get back to his battery.
 
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LONGJP2 said:
Yes, it does seem it would have to be a short directly to a brake line. A short to metal (ground) would have no reason to go through the brake line to get back to his battery.
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It likely isn't shorted directly to the line. It is using them to find a ground and they are connected to the firewall via master and booster.
 
Maybe take the winch completely off the vehicle to see if that is the source of the ground, could be an internal problem with the winch motor itself.
 
mrblaine said:
It likely isn't shorted directly to the line. It is using them to find a ground and they are connected to the firewall via master and booster.
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The OP indicated the body and engine grounds are good (to the battery). Didn't mention a frame ground.
Unless the grounds aren't large enough to handle the amps, I don't see why it would need to look for a ground path through a brake line back to the battery.
 
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LONGJP2 said:
The OP indicated the body and engine grounds are good (to the battery). Didn't mention a frame ground.
Unless the grounds aren't large enough to handle the amps, I don't see why it would need to look for a ground path through a brake line back to the battery.
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Here is what we know. The brake lines were used as a ground path. That doesn't happen when stuff is correct.
 
Jerry Bransford said:
When stuff is not correct it can happen even if everything is properly fused. I still believe it was caused by ground scavenging.
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Jerry, what would draw enough current while driving down the road to get the brake lines hot enough to start a fire caused by them serving as a ground path? I would expect the brake lines to easily carry 20 or 30 amps without even getting hot and I doubt the whole electrical system is drawing that much while just driving down the road.

That's what I cannot figure out and why I don't think it could be a ground problem. I would think the highest current draw while driving down the road would be headlights (assuming non-LED). Aside from headlights, the engine, computer, miscellaneous stuff would not seem to be a big enough draw to heat up brake lines anywhere near that much. Of course, I could be totally wrong.

Maybe if you had some crazy high-power audio system but no mention of that from the OP.
 
That's what I cannot figure out and why I don't think it could be a ground problem. I would think the highest current draw while driving down the road would be headlights (assuming non-LED). Aside from headlights, the engine, computer, miscellaneous stuff would not seem to be a big enough draw to heat up brake lines anywhere near that much. Of course, I could be totally wrong.
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A winch that has malfunctioned so that the winch is on and pulling , the winch line is pulled tight then the motor will take all the current the vehicle can give and if the ground wire is not up to the task (for whatever reason) the winch will try to return any way it can, with all the current.

This is why I make sure our winches are always disengaged when not in use as I have seen several winches "shortout" is just this way and one burn our deer lease truck to the ground.
 
g.hayduke said:
Jerry, what would draw enough current while driving down the road to get the brake lines hot enough to start a fire caused by them serving as a ground path? I would expect the brake lines to easily carry 20 or 30 amps without even getting hot and I doubt the whole electrical system is drawing that much while just driving down the road.

That's what I cannot figure out and why I don't think it could be a ground problem. I would think the highest current draw while driving down the road would be headlights (assuming non-LED). Aside from headlights, the engine, computer, miscellaneous stuff would not seem to be a big enough draw to heat up brake lines anywhere near that much. Of course, I could be totally wrong.

Maybe if you had some crazy high-power audio system but no mention of that from the OP.
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Nothing normal in a proper functioning system will be a problem. The way you know you have a problem in a dysfunctional system is the brake lines got red hot because they were in a high amperage ground path.
 
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I would disconnect the wiring from every add on I could think of. Get the Jeep back to as basic as you can electrically. Then see what happens. Then start connecting things back in if it works. Break it down to its most basic form.
 
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TJ Jeepers. Update. Unfortunately, I have not been able to make the time to continue my troubleshooting of the TJ as a result of my career, life and helping someone complete their up-fit of their new business space. I will be flying out of town on Monday and will not return until the end of February, at which time I should be able to continue the hunt for Mr. Sparky and the mystery of the glowing brake lines. Until them, best wishes and I'll write back once I have time to get back under the hood. Regards,
 
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Hello Jeep Fans, I'm back and hunting Mr. Sparky.
Having been out of country for the past few months I was finally able to start the trouble shooting procedures as provided by G. Hayduke. Here's what I found and where I"m currently at in the troubleshooting process.

Having tested the negative lead paths for engine, frame and body, we have a good ground with new larger wires. The positive lead wire from the battery to ground was showing a short. From this point I started removing relays and fuses to isolate each circuit, but found no fuse or relay that opened the circuit. I removed the battery, disconnect all positive lead wires from the starter to the alternator, then started testing from the alternator positive lead to ground. I still had a short from the alternator positive lead to the body of the alternator. This lead me to believe my alternator had a dead internal short. I removed the alternator, put in on a test stand at a local parts store and it failed test. Great new I had a bad alternator!!! However, before replacing the alternator I was concerned something else drove the short, causing the brake line to turn red-hot and damaged the alternator. I continued my troubleshooting to ensure I had identified the problem before installing a new battery and alternator. Bad News??? During my continued troubleshooting I found another dead short to the positive side of them main fuse box, where the two 10mm studs are. With all positive lead wires removed from the fuse box, meter connected between the positive post on the fuse box and the meter negative lead connected to ground on the frame I got a short when I turn my ignition key from the locked position, through the accessory position to the start engine position. Yes, when ignition key in the off or accessory position I am not showing or getting a tone for short. When I rotate the key to the start position I get a tone indicating a short. I then returned to the fuse box and removed the 20 amp fuse for the starter and the tone end, I opened the circuit. I replace the fuse and got the tone, but disconnect the wire going to my starter relay and the tone continued.

Current situation: I am showing a short between my ignition keyed switch to one terminal lead of the 20 amp fuse slot. With the fused removed I can test the copper color connector to ground, no tone. When I test the other fuse connector pin, silver or common color pin, I get tone on my meter. Therefore, I believe I have a short in the wiring somewhere between that common fuse pin and the ignition switch.

I have identified which wire bundle connector at the steering column has this wire in it. When I am getting a tone I can unplug this black connector from the switching plastic thingly at the column and the tone ends. I will start ringing out the wires from this black plus to the common colored terminal at the fuse box. At some point I should get a tone when I identify/touch the right wire. At that point I will start tracing this wire from the connect back towards the fire wall. Being this wire bundle arches over the steering column and flex any time the steering column is adjusted up or down I"m sure their is some chafing going on. In addition, when I opened up this area of the steering column I also found as some one in time someone had been in this area to splice in/connect an anti-theft device.

I think I'm on the right path, but it has now started raining here in North Carolina so I called it quits, but knew I owed you all an update.

Having done my best to highlight my troubleshooting process does anyone have any other recommendation for this new discover of the short to ground when I turn the ignition switch to the start position?

Thanks everyone for your help.
 
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Result of troubleshooting yesterday, 03-15-2020.
Back to turning the ignition switch from accessory to start I get a short from power plate of fuse box to ground, in this case my terminal clap is attached at the brake line. I can pull the 20 amp fuse from the fuse box and the short goes away, I have broken the circuit.
While looking for a possible bad wire I found I also get a short, or tone on my meter, when I pull my turn signal handle to the aft position as to turn on my bright lights. I can eliminate this tone by removing the 40 amp fuse that powers all the lights.

So, with both fuse installed in my fuse box I'm getting a short indication from my power plate of the fuse box to ground. I can disconnect the wire connector at the turn signal switch and ignition switch and identify the wire giving my the short tone. However, I have not been able to identify any place along the wire harness where the wires might be making direct contact with metal, the wire seem to be insulated.

Where do I go from here?
 
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