oamhmad

iTrader: (1)

I had a massive short at the starter that fried the negative battery cable and melted the post on the battery!

When I switched to an LT1 starter I left the rear support bracket that supports the larger stock starter, bolted to the block. Big mistake. Every now and then, I noticed that all electronics would go dark for a second when I accelerated real hard from a stop. Never could figure it out, until today.

I hit the gas real hard and the bracket must have pivoted backward on its mounting bolt. It contacted the power post on the starter and shorted the heck out of everything. It actually welded itself to the starter post and by the time it took me to stop the car get out and pop the hood the negative cable has already melted itself off the battery post.

So I need a new battery and cable. Problem is, I've removed the offending bracket but I still have a short somewhere. I removed the battery and hooked a micrometer across the remnants of the negative cable and the positive cable.

I did not see infinite resistance, it was pretty high, but not infinite, indicating there is still a short from the negative cable to the positive. Any ideas where to look?

I hope the starter or alternator are not fried.

TreeFiddy

If reistance was pretty high, then there is no short. There will probably be some full-time parasitic load like the clock in the radio etc which would show as a high impedance but not infinite.

OTOH, the ground cables, the batt + cable to the starter, and all terminals involved just took a massive beating. I would replace the whole lot, even if it works for the moment you'll probably have reliability issues later.

Starter and alt are probably fine, as they were not in the path of the short.

Six_Shooter

iTrader: (2)

^^^ This

Electrical components will measure some amount of resistance, when connecting a multimeter across the positive and negative terminals, some will even read a dead short, due to some of the input protection used.

What causes you to say there is still a short in the car? Is there a slight spark when connecting the battery cables? Often this is normal, because it is charging the power supplies, more specifically the capacitors used in those power supplies in the electrical components.

If you have an aftermarket audio system, especially on with a stiffening capacitor, you will get quite a large spark when re-connecting battery, after discharging the stiffening capacitor, if not charged slowly.

If switches for the lights are left on, or a door is open, a large draw can be seen, because of the load from the lights themselves.

mwarner44

Hook up a test light and pull the fuses one by one until the light goes off, then that is the circuit that is shorted. If the light stays on even after all fuses are pulled, then it is probably the alt or starter. They are easy to take off, so just take them to autozone and have them tested.

If none of the above then it is probably some random positive wire somewhere making contact with a ground. Good luck finding that.

Six_Shooter

iTrader: (2)

An electrically proper vehicle will still light a test light when connected between a battery cable and the battery.

There are circuits , such as radio memory and ECM battery circuits that will have a constant drain.

mwarner44

If he disconnects the negative battery cable and connects the light from a good ground to the negative battery post, a short will activate the light. The light shouldn't have power when only connected to a ground source.

Six_Shooter

iTrader: (2)

Incorrect.

With the items that need battery power, there will still be current flowing, this WILL illuminate the light, when placed in series with the battery connections.

This comes down to voltage potential.

Do this, go out to your car, disconnect the negative battery cable, and then connect a multi-meter set for 12V reading, between the negative battery cable and the negative battery terminal, you will read 12V positive on the negative battery cable, because the voltage potential flows all the way to the end of the open circuit.

Next step, place a test light in place of the multi-meter connection, and you will see it illuminate.

oamhmad

iTrader: (1)

I'll install a new battery and if there is a huge spark then I'll know there is still a short somewhere.

The path the current took looks like it was from the battery positive straight to the starter post where it shorted to the block and then from there back to the battery via the negative cable from the alternator bracket, frying the cable in the process.

oamhmad

iTrader: (1)

Replaced the battery cable and hooked up a new battery. Everything is back to normal! I guess you guys were right about the impedance across the positive and negative battery cables.