Sounds like a regulator problem. Quick test...run the truck and put a volt meter on the batt post. If it reads over 14v its probably overcharging 15-17v. Most shops have a AVR machine then you will no for sure. If you have a problem with the Reg. or Alt. now would be the time to think about getting rid of the external Reg. and thinking about a 1 wire internal regulator high amp alternator. I put a Powermaster in my 69 and never looked back
