Electrical short causing brake lines turn red hot and starting fire

ArmyMohawk269

ArmyMohawk269

New Member
Joined
Feb 4, 2020
Messages
13
Location
Mooresville, NC
Need help!, 2004 TJ. It appears I have an electrical short causing my break lines to act as the grounding source which turned them red, yes red glowing hot, setting fire to the plastic stand-offs. When this occurred I a got a check gauge light, I saw my alternator gauge go to 9 volts, when I pulled over and shut off the engine I popped the hood to find a fire under my master cylinder where the four break lines pass through the plastic stand-off. The battery cables and battery were super hot and battery discharged completely within 45 second of turning off engine.

I can not find any melted wires, or smelled any wires burning. I have good grounding wires connected from batter to engine block and fire-wall. I have not found any wires grounding to the brake lines anywhere under the jeep.

Where should I go from here?

PS, Luckily I broke down just down the street from where I live and got another Jeep to pull me home, saved a little face.

Thanks everyone for your help.

ArmyMohawk269
 
ArmyMohawk269 said:
Need help!, 2004 TJ. It appears I have an electrical short causing my break lines to act as the grounding source which turned them red, yes red glowing hot, setting fire to the plastic stand-offs. When this occurred I a got a check gauge light, I saw my alternator gauge go to 9 volts, when I pulled over and shut off the engine I popped the hood to find a fire under my master cylinder where the four break lines pass through the plastic stand-off. The battery cables and battery were super hot and battery discharged completely within 45 second of turning off engine.

I can not find any melted wires, or smelled any wires burning. I have good grounding wires connected from batter to engine block and fire-wall. I have not found any wires grounding to the brake lines anywhere under the jeep.

Where should I go from here?

PS, Luckily I broke down just down the street from where I live and got another Jeep to pull me home, saved a little face.

Thanks everyone for your help.

ArmyMohawk269
Click to expand...
Post up a pic of the top of the battery.
 
  • Like
Reactions: Chris
Attached are two pictures of the battery, note the negative wire is disconnected as well as a few other wires. I also include a pic of the battery capacity data. Thanks Mr Blaine.

Battery Top.jpg


Battery Data 1.jpg
 
Sure sounds like a short to a brake component somewhere. And sounds like the source is unfused and high-current. Seems like it should not be that tough to find.

Does your Jeep have ABS? I'm just wondering if something in the ABS system could be the source of the short. Does your Jeep have any electrical modifications that you know of?
 
G. Hayduke, thanks for taking the time to reply. Likewise, I have looked for a large wire/cable able to carry such a current without a total meltdown. The only wire harness no totally accessible is a harness running aft, passenger side from the under hood fuse box, down the firewall taking a turn over the backside of the engine, moreover the transmission housing. I've also looked around my steering column knowing this could be a pinch point with an adjustable column, no finds noted.

Only electrical modification:
Installed winch - inspected cables no findings, disconnected cable to eliminate source, still getting short.
Eaton E-locker - The routing of this cable runs along side the brake line going to the rear end. I have followed this wire run and have not found any defects, pinch points. In addition, the fuse for this unit is not blown, which makes me think it cannot be the source.

Could something in the ignition switch be bad? Making contact with the steering column and transferring electrical power to the brake master cylinder at the fire wall?

Here's something I tested, is this a good test. With my multi-meter set at VDC I connected the positive power cable to the battery. With the negative cable disconnected I connected the positive meter leads to the negative post on the battery. Then touched the negative meter lead to any metal on the frame, engine, master cylinder. When I do so it show 11.6 VDC between the battery negative post and the component. Should I be getting a VDC reading when jumping between these points? I believe this is showing I have a positive cable short making contact with the ground frame.

If you connect the positive battery cable as usual, then try to connect the negative cable to the battery you get an immediate spark telling me I have something pulling power and with all components turned off that indicates a short.

Does my thought process make sense?
 
ArmyMohawk269 said:
G. Hayduke, thanks for taking the time to reply. Likewise, I have looked for a large wire/cable able to carry such a current without a total meltdown. The only wire harness no totally accessible is a harness running aft, passenger side from the under hood fuse box, down the firewall taking a turn over the backside of the engine, moreover the transmission housing. I've also looked around my steering column knowing this could be a pinch point with an adjustable column, no finds noted.

Only electrical modification:
Installed winch - inspected cables no findings, disconnected cable to eliminate source, still getting short.
Eaton E-locker - The routing of this cable runs along side the brake line going to the rear end. I have followed this wire run and have not found any defects, pinch points. In addition, the fuse for this unit is not blown, which makes me think it cannot be the source.

Could something in the ignition switch be bad? Making contact with the steering column and transferring electrical power to the brake master cylinder at the fire wall?

Here's something I tested, is this a good test. With my multi-meter set at VDC I connected the positive power cable to the battery. With the negative cable disconnected I connected the positive meter leads to the negative post on the battery. Then touched the negative meter lead to any metal on the frame, engine, master cylinder. When I do so it show 11.6 VDC between the battery negative post and the component. Should I be getting a VDC reading when jumping between these points? I believe this is showing I have a positive cable short making contact with the ground frame.

If you connect the positive battery cable as usual, then try to connect the negative cable to the battery you get an immediate spark telling me I have something pulling power and with all components turned off that indicates a short.

Does my thought process make sense?
Click to expand...
Sounds like the winch is looking for a ground and using the brake lines to supply it.
 
@mrblaine, if the winch is the issue, and with the power cables not showing any external damage it would have to be an internal short of the motor windings, correct? If so, I should be able to disconnect the winch power, then test for power transfer from the batter to the frame by connecting the positive power cable to the battery, leave the negative cable disconnect and place my meter between the negative post of the battery and any ground component of the frame and not see VDC registering on the meter? If I see VDC on the meter I still know something is shorting to the frame? Thoughts...
 
Are you absolutely 100% certain the winch's black ground cable could never have been connected to the tub or chassis when it was in use?

Or has there ever been a disconnected (or a bad connection at a) ground strap at the chassis/engine, especially while winching?

Your symptoms sound less like a short and more like a missing major ground connection.
 
Last edited:
Jerry Bransford said:
Are you absolutely 100% certain the winch's black ground cable could never have been connected to the tub or chassis when it was in use?

Or has there been a disconnected ground strap at the chassis/engine?
Click to expand...
Thanks for the question Jerry. I have inspected and verified the following related to grounding. The braded flat grounding cable coming from the left side of the engine to the firewall then looping to the hood is securely connected and in good shape. The grounding cable from the battery to engine block grounding stud is secure and the grounding cable from the fire wall to the negative battery post seem to be secure, serviceable and no notable outward damage or defects in insulators.

I will however, go back and look once again at the cable run to the winch. It's a very short run, mostly visible, but I will check again.

Thanks again for your recommendations.
 
  • Like
Reactions: Jerry Bransford
X2. Rather than a short. 12v looking for ground. If it doesn't have it properly it will find it wherever it can( if it's available ). And pull lots of current!
 
  • Like
Reactions: Jerry Bransford
ArmyMohawk269 said:
Here's something I tested, is this a good test. With my multi-meter set at VDC I connected the positive power cable to the battery. With the negative cable disconnected I connected the positive meter leads to the negative post on the battery. Then touched the negative meter lead to any metal on the frame, engine, master cylinder. When I do so it show 11.6 VDC between the battery negative post and the component. Should I be getting a VDC reading when jumping between these points? I believe this is showing I have a positive cable short making contact with the ground frame.
Click to expand...
If I'm following you correctly, that is normal. Testing across a short (like a fuse) reads 0v. Testing across an open (like you're doing) will read the difference in potential, 12V.
Edit: Normal unless everything is turned off; including radio memory, pcm, etc.

Also, an intermittent problem might not show up when the vehicle is not running /vibrating.
 
Last edited:
  • Like
Reactions: g.hayduke, Mjv and Jerry Bransford
I don't think you have a ground problem. I think you have a dead short somewhere from something connected to the positive battery terminal to your brake lines.

I would start with these steps:
1.) Verify good grounds. With negative cable disconnected from the battery, check continuity from the battery end of the negative cable to various places that should be grounded. Check continuity to the engine block, tub, frame. Ideally, you should see 1 ohm or less but 2 or 3 ohms is probably OK.

2.) With the positive battery cable connected but leaving the negative cable disconnected, start checking continuity from the positive battery terminal to various grounded points, similar to above. You'll probably see a dead short or close to it. It's normal to see some connectivity through various electronic components but less than a few ohms indicates a probable short.

3.) Assuming step 2 indicates a short, start disconnecting things to eliminate them as a source of the short. Do this by pulling fuses, disconnecting grounds, etc. Be methodical. At some point, when you disconnect something, the short will disappear. That will tell you whatever you disconnected was either the shorted component or it's connected to the shorted component.

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.
 
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.
Click to expand...
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.
 
Last edited:
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.

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.
Click to expand...

I totally agree with everything you said but it's applicable only when the winch is operating. If I understood the scenario described, he/she was just driving down the road......

When the winch is not operating, the winch ground carries no current whatsoever....
 
Gentlemen, I appreciate everyone's efforts to get my TJ back on the trails and can't believe I've gotten advise so quickly.
G. Hayduke, I will follow your recommendation and start the trouble shooting process as soon as possible. The direction you have given will put me on the right path to surely find the problem.

Update, while looking at the brake line routing across the front of frame tube/structure and verifying no wires were contacting the line I continued to look at other areas. In an earlier post I mentioned about getting a spark when I tried to connect the negative ground wire to the battery. The battery does have power as I've charged the battery. All of a sudden the arcing has disappeared when I try to connect the negative lead. Could these be an issue found only when a relay is in closed position. Maybe the relay reset to the open position? I was in my dash area moving wires from the radio, overdrive lock-out switch, temp control head.

Electricity is hard to chance. I'm sure with everyone help I will find it.

I will report back later when I have time to follow G. Hayduke's trouble shooting recommendations.
 
Good luck and please provide updates as you work through it. Honestly, sounds like a fun problem to solve. Sorry your Jeep is down though.

Thinking about all the good comments, since the winch is the most obvious un-fused, high-current component you probably have, I agree it's a good place to start looking. But unless the problem started either while winching or shortly afterward, I would focus on the positive cable feeding the winch and any winch connections that would be energized even when the winch is not operating.

Something was pulling high current while you were driving down the road. There is not much that should pull that kind of current while driving. That's why I suspect it's a short to ground, probably directly to the brake lines or a braking component.
 
Top Bottom
Back