Melting Battery Cable

Over the past year or so I have noticed that when I press the clutch on my 1985 CJ-7 258 that the headlights would get brighter. This happens when driving or just sitting at an idle. This happens only after you press the clutch enough to take up the usual 1/2-1 inch of play in the clutch pedal. When you release the pedal, the lights dim slightly. Another thing that may be related—over the past few months, it has been a bit sluggish to start until, finally, it wouldn’t start at all. I looked at the battery and the cable connector on the negative battery pole is partially melted and ran down onto the top of the battery. Any idea what the problem might be? I’d hate to get a new battery and just have the same thing happen again. Thanks!


Clean and check all connections and get the battery checked. You probably need a new battery.

Clean all connections and make sure they are tight. Before replacing the battery, have it load tested. I’m assuming when you say it’s sluggish to start, that the engine cranks slowly when you turn the key. That and the melted insulation makes me think you may have a failing starter motor that is drawing an enormous amount of current.

As far as the headlights getting brighter when you push the clutch, all I can think is that the engine or transmission or both move somewhat when the engine torque is released and this causes a poor connection to get better–check the connections at the starter. On a lot of older cars the starter was used as a main junction point for power distribution. Also check the ground straps from the engine to the body and battery to the body.

I think that the ground strap between the engine and the chassis is either missing or there is corrosion on one end or the other. When you depress the clutch, you complete the ground. The engine is isolated from the chassis by the rubber motor mounts. Run a heavy wire between the chassis and the engine block and this may solve your problem.

My thot also is that the ground straps are missing or corroded.

They’re right, it’s a grounding problem and the battery cable that melted is part of the problem. The other grounds are necessary but if you’re lucky the old battery cable in deteriorated condition may have been the main problem. I have seen a loose battery connection start to smoke and melt like your battery connection.

The melting of the connector most likely happened due to a dirty connection to the battery post and the resistance caused heat to build up from the current flow through the resistance. You may want to replace the cable if the melting is severe enough. Clean all the engine and chassis grounds under the hood.

I’m still sticking with my bad starter motor theory. There are probably multiple poor connections that need to be addressed on this elderly vehicle’s electrical system, but with a poor connection, the connection will heat up at the point of resistance. Since the insulation on the cable itself melted, I’m still thinking the starter was drawing an enormous amount of current through that cable.

Anyway, I hope the OP posts back once he solves the problem.

1985? I’m going to digress. I’ll bet lunch that the wire that melted was the fusible link that went to the underhood fuse/relay box. It looks like a wire, but is actually it’s a rated fuse.

The reason it blew is that you have a short or excessive current draw somewhere. It could be in the starter motor solenoid, but could be elsewhere as well. That wire is the main feed to everything other than the actual starter motor. In addition to feeding all the other circuits, it feeds the voltage to the starte solenoid. The contacts in the starter assembly are then closed and allow a direct feed from the battery to the starter motor through the heavy cable that co-connected to that battery terminal.

Do NOT replace that link with a regullar wire. You could light the Jeep on fire without that protection. Go to a parts store and get the correct replacement.

One clue you might get is if you have another fuse blown under the dash. That might suggest a specific circuit with a problem.

@the same mountainbike: I guess it depends on whether the system is still operative after the “melting incident” or whether it is now dead. If it was a fuse link, everything should now be dead.

I had a Ford with a bad starter that melted insulation on the cables between the battery and the solenoid (on the fender) and the solenoid and the starter. Not enough to destroy the insulation and require replacement, but enough to smoke. I initially thought I had a bad battery, but saw smoke rising from the battery area just as the engine caught–it had stalled on me in the middle of the street. Fortunately the shop where I’d planned on having the battery tested was a block away, and they also sold starters. The battery was a 1200 CCA model that was under a year old and apparently wasn’t giving up before the wiring did… I was younger and dumber then.

My experiences with this vehicle and a couple others led to me becoming disenfranchised with Fords, but that’s another story.

I suppose the OP is long gone, so we’ll never know how this turned out, but so it goes…

connect a 10ga wire from the battery (-) to the base of the fender mounted starter solenoid.

All this is very helpful. It was actually the metal connector on the negative terminal that melted and dripped molten lead on to the battery. The insulation was fine. I’ll be checking all of the connections and grounds. The starter is a “Mean Green” brand that I purchased new about 2 years ago, but I’ll have that and the battery checked as well. I’ll give feed back when I find-out what the problem is. Thanks again!

Ahh. The way you made it sound was as if the cable was melted, not the terminal.

You’re welcome for the help. The problem was due to a faulty/dirty connection on the negative battery post.

I replaced the negative battery cable and charged the battery. I could find any loose or dirty connections except for the ground wire. The ground wire connecting the engine to the frame was dangling in the breeze and broken off on one end, so I replaced that as well. The Jeep fired right up. The starter has never been so spunky and the lights don’t change anymore with pressing the clutch—it’s totally fixed! Thank you so much.


Good find on the open ground wire. Thanks for the update.