I ran new grounds. From each battery to the stock ground point, another from each battery to the screw that holds the front of the battery hold-down, and another from each battery to the ground point for the alternator on the front of the motor. Last night I had the headlights on without running it for about 15 or 20 minutes, when I fired it up to come home it jumped right up to 16 volts. After about 2 miles it dropped right to 12 and the headlights seemed dim, then it came up to about 13 and stayed there. What's next?

 

My truck has a big ground going from the battery to the radiator support, maybe that'd help.

 

Are your grid heaters still hooked up?

 

discharged the battery in 15-20 mins of headlight usage. Is the battery new or old? Sure doesn't seem like the grid heaters would be kicking in, not cold enough there is it?

 

How rusty is your truck? I'd run a ground from a regulator screw to the engine.

 

I'll try the regulator ground. I have wire and terminals. This thing came out of Texas, there isn't much rust anywhere. I did have the trans cooler go bad so everything under the hood has been soaked in oil.The grid heater's haven't cycled in the morning since May. Seems if one battery was bad it would down the other but the only no-start I had was loose cables. I cleaned the terminals when I ran the new grounds, too. It's like it jumps to full output for a few then drops to where it should be.