1979 GMC K3500 - No electric.
 

I am having a problem in that I don't have any electric on the truck. When I turn the key I am getting nothing. Turn on the lights - nothing. Radio - nothing. Etc, etc, etc.

Battery is at 12.7 volts. Ground line seems to be working ok.

I did get some intermittent times that I had things come on. But, it seems impossible to replicate the conditions.

Any thoughts?

Is the positive terminal connected ???? Attachment 2501

check your battery terminals they may be loose
 

check them they may be loose if they are loose they will cause that problem. also check the terminals themselves to ensure they are still tight cuase if they are loose on the baterry post it will do the same thing.
then check the wires to make sure they arent loose anywhere it is an older truck

I have had both terminals off and they both are tight and the is no corrosion.

There is full voltage on the battery side of the coil.

check the harness leading to the starter motor, you should find one or two fusible links