Grounding Problem

[BigRandy]

My 74 C-10 has an odd problem - odd to me anyway.

Battery has 13+ volts. Cables are clean and tight.

It will usually start fine but sometimes cranks like the battery is weak when it isn't, and the #10 wire from the battery gets smoking hot which tells me it's trying to use that as ground.

The #10 ground wire on the neg post is bolted to the frame which I'm guessing is normal. The 2ga negative cable is bolted to the alternator bracket. Connections have been checked and cleaned. The 2ga cable looks great.

I removed and cleaned the braided strap from the motor to the firewall. Anything else I can check?

I thought bout running another 2ga wire from the alternator bracket to the frame next to the #10. That should give the motor and frame enough ground to work but that isn't the right way to fix it. It's got me puzzled - the starter is bolted to the motor which is grounded at the alt bracket. That should be enough but I think I'm missing something.

Thanks!