Are you running this plugged in only with no battery in the system or just battery? I would guess you're plugged in, which case if you have a battery installed the univolt is probably boiling your battery. The univolt is what converts your power to 12v
from 110. On a 69 if yours is like ours its a blue box wired in the compartment (passanger side) under the wheel weel/tub area. Worth checking to see if you get more than the usual voltage at those terminals. If so I would guess the unit is fried and would disconnect it before you damage any electrical items. We installed a intelipower with charge wizard at the recommendation of users on here. It is absolutely quiet (no hum) and helps keep the battery in check.