wires sparking on battery

[1lo620]

Ok I have been do a little work here and there on my chop top. I went to try to start it the other day and when I hooked up the batter cables the positive side it sparked and started to smoke. Now the wire harness is out of a 76 620, but I put the who;e harness in the truck from front to back. I no issues with it in the 76 when I drove it. am I missing a ground issue somewhere? I am for sure not a mechanic, but I also know it shouldnt smoke when I put the cables on the battery...

Any of you datsun crazed mechanics have any suggestions of what to check. I would prefer to try to work it out myself, so any help would be greatful..Thx..

[izzo]

That is weird, does it just smoke for a second or continue? I would assume there is a hot wire touching the body or something somewhere.

[datzenmike]

Remove all the fuses and try again

 

Unplug the alt. and the regulator.

[MicroMachinery]

Check your connections. Bad connections increase the resistance. The more resistance, the more heat. Corrosion or anything like that can cause your cables to get hot, or even melt. Check your grounds, too.

[datzenmike]

Something is drawing power that shouldn't. Nothing should be on without the ignition key on.

 

There is always power to the headlight switch... so headlight, tail lights and marker lights can be turned on.

There is always power to the interior light.

There is always power to the horn.

There is always power to the 4 way emergency flashers.

There is always power to the clock if equipped*.

There is always power to the brake lights

There is always power to the alternator output wire and the external regulator.

 

 

* This is the only thing that should be drawing any power with the key off.

[Unclejesse88]

Check your starter cable. Sometimes aftermarket cables are larger than stock and can ground out on the starter case. For it to be a large arc that smokes, (and maybe get a bit of metal transfer from the terminal) it needs to be a large draw. On a side note, I'm a fan of hooking up the positive cable first, and the negative cable last. This way when you are wrenching on the positive terminal, your wrench can contact anything besides the negative terminal and nothing will happen. If you hook up the negative first, if your wrench contacts anything metal while you are installing the positive terminal, it will arc.

[yello620]

I have to agree here that the negative cable should be hooked up last(and removed first).

 

The other thing that needs to be done here is to test for a system draw with a test light so that you are not chancing it each time you hook up the cables.

 

With the negative battery cable removed from battery, attach the positive cable to the battery. Now put an automotive test light between the negative battery cable end and the negative battery terminal. If you have a system draw the light will light up. The brightness of the draw can help determine how big the draw is.

 

Now with the test light lit up, pull fuses(one at a time), alternator wiring, ignition switch connector. Until the light goes out. This will isolate which circuit has the system draw in it.

[1lo620]

thanks all I will do some testing and checking and see what I come up with, and I will let all know what happens..