CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Negitive battery terminal melted

While reinstalling my battery after working on my 94 sentra my negitive battery cable melted my negitive terminal.

I installed the positive first then went to do the negitive and huge spark/smoke and I see my terminal melted on the one side.

Any idea what might be causing this?

What part were you working on?

I think you caused a dead short when you were working on the car.

Yosemite

First thought is a direct short, make sure the pos cable is not shorting to ground.

Good thing you were not working on something with a thousand volts…or we’d have to call you
"No Pulse"

Yosemite

I just finished a clutch/flywheel replacement. So I had air box, starter, clutch cable, shift support/control driveaxles and transaxle out.

Can you explaine what a dead short is?

Check your work.

You’ve almost certainly attached the battery cable that SHOULD go to the starter in such a manner that it is contacting something else on the car.

Make sure the positive starter cable connected to the starter terminal, not the engine block.

I’d look first in the area of the starter and make sure you hooked it back up correctly. Of the items you listed it’s the area most likely to be where the problem is. An example of a dead short would be if you were to somehow crush the positive cable pinching it between two parts when reinstalling them it would cause a direct short to ground which is where the negative battery cable goes.

A really basic example of a dead short would be if you were to take a battery cable and connect one end to the positive terminal and the other end to the negative terminal. Of course that would never happen.

So I found the issue I believe. There was a hole in my negitive cable and it was touching the positive ground on the starter. The rubber end cover is pretty much worn and there is a bit of exposed wire were the copper attaches to the ring. I think I made a pretty big mistake though because now the car won’t start. Ill do some checking of things tomorrow morning. It cranks just doesn’t start. The last go i held it for a few seconds longer and it sounded like it wanted to kick to life but i didn’t want to try and force it so I quit for the evening

Also should I get rid of the battery i melted a bit of the post on?

Dead means complete this time. It’s like saying dead stop. Dead on.

Check fuses and fusible links.

“Also should I get rid of the battery i melted a bit of the post on?”

If it measures 12.6V and cranks the engine over, it’s probably OK.

Not sure what you mean by “positive ground on the starter”. But I assume you had short from battery positive to battery negative, via the big thick wire that is bolted directly to the starter. So the damage (smoking, heat) occurred as soon as you connected the second connection of the battery.

That by itself shouldn’t prevent the car from starting now. I’m wondering if a grounding point got burned and corroded, like the ground between the engine and the chassis. That’s worth checking.

If other circuits were involved in the short, then almost anything could have been damaged. Certainly makes sense to first of all check the fusible links, then all the fuses in the various fuse boxes.

The only other thing I can think of is that when you disconnected the battery after you noticed this problem, it created a big voltage spike and that could have damaged something in the ECM. I don’t think that is the most likely explanation though.

Just a side note, a guy a few miles from here burned his fully restored vette to the ground a few days ago. Put the battery charger on it, went in the house for a few minutes and came out to flames. Most likely he hooked the negative up to the battery and not another metal part and caused the hydrogen to catch fire maybe. Dangerous things, batteries.

It sounds to me like you have something hooked up wrong. I think you attached the positive cable directly to the starter housing…not the positive lug on the starter.
There is no ground wire to the starter. It is grounded through the mass of the engine block.

Had you stopped when trying to hook up that last battery connection when it sparked, you may not have done much damage. You should only get a very small spark while installing a battery, from the memory modules and under hood light.

I’ve never seen a ground from the battery come close enough to the starter to cause a short. The ground cable usually runs directly to the engine block and I’ve never seen one long enough to even reach the starter.

I think you may have attached the positive cable that runs to the lug on the starter, to the wrong bolt and caused the dead short as soon as you touched the negative cable to the battery terminal.

Yosemite

George. Im not sure what the other end of the positive cable is called but it looks the the negitive ground so I just called it that lol. But it’s the part of the positive wire that goes on the starter post.

Yosemite
I know it’s weird but my neg cable is about 2 ft long and is suppose to ground to the starter bolt that attaches to the starter to the engine.

I attached a photo of the wire on its way to the starter above the transaxle what happened was I ran the negitive wire over top the positive and there was bare wire touching from the neg touching the positive cap. There’s a little rubber cap on the positive wire to starter end of the positive cable this cab was destroyed so it was an accident waiting to happen and a very dumb mistake.

Here’s a pic of the neg cable running to the starter

I’ve never seen a ground line go to the starter mounting bolt, and it’s probably for just this situation. There’s no reason why it should go there that I can think of, since the metal to metal connection between the starter and the block is very solid. You might want to move that end of the ground cable to some other solid mounting on the block.

I’ll second @Wentwest; and say that you can always find a tapped hole on the block somewhere…away from the starter and the positive cable.

I think someone else may have routed it this way because they were having trouble with it starting.
Then they finally cleaned the battery terminals and never thought to rout that ground wire back to where it originally was.

Yosemite