got another electrical issue with our 78 chevy pu... I'm guessing maybe its a short in the lighting system. Occasionally the battery will run down and not recharge while driving.. This only happens at night when the lights are on which leads me to believe its not the altenator (that and I had it tested). The other thing thats aggrivating is that it doesn't happen all the time.. only occasionally like maybe once a week. My question is how I would check the circuit?