Went out to drive my 69 convertible last week and it was dead as the proverbial door nail. It was just fine the previous day. I only drove it about 15 miles that day, and it was one of the few times I’ve used the headlights. In fact I forgot to turn them off, realized it when I got out and saw they were still up, started it back up, turned off the lights and made sure they closed, shut it off again. When I realized it was really dead, not loose cables ( negative cable has a propensity to loosen itself) I was surprised but the battery was a few years old. Put it on the charger overnight and next morning it still shows less than 10% charged. Time for a new battery I figured. Got a new premium battery, installed it and all was good. Drove it around for about an hour. Gauge showed charging mildly…about normal. Next day about 11 hours after I parked it… dead as the proverbial door nail again. Put it on the charger until it showed 100%, tried it and all was well. Next day… dead again. Obviously I have a huge drain that probably started that day I had the headlights on. Not saying it is a headlights issue but it’s the only unusual thing I did. All wiring is original so with that many years it could be anything. Looking for input on first place to start looking for the drain from those who might have encountered a similar problem….

 

First thing I would check is to see how much, if any, voltage your alternator is producing. Jerry

 

Unfortunately an Alternator can have a bad diode and charge just fine. A diode allows power to go one way but not other. Sometimes a diode fails in such a fashion it allows power to go both ways. So power goes out while alternator is spinning. But flows the other way when shut down, draining your battery. An Amp meter is your friend when chasing a drain. But you might try unhooking the wires to the Alternator for a day and see what happens.

 

Check to make sure all lights inside and out are off. Check in A Dark garage or at night. I discovered the infamous rear “glove box” light was not turning off Even when the door was shut and latched. I adjusted the latch and added a rubber bumper, but the bulb/ switch doesn’t allow very much room for play.