Found the battery dead on my 86 two weeks ago. The 27K original car sits in the garage, and is started up and driven once a week. It's completely stock, except for a remote CD changer that pulls it's power from the factory power feed to the stock radio. There was nothing left on to discharge the battery. The battery charged up quickly, and has been holding it's charge since. At first, I figured it was a bad cell in the battery, or a cracked diode in the altenator discharging the battery, but the fact that it has stayed charged for a week at a time for the last two weeks blows that theory out of the water. Any ideas as to what could have discharged it? Thanks in advance.

 

Well for starters, is it the original 20+ year old battery?

 

Not sure what years switched from a carb pickup in tank to a fuel pump in tank - but if you have an in-tank fuel pump, try listening for the fuel pump when the car is off. Fuel pump is controlled by the Oil Pressure Sending Unit, and it can go bad in such a way that makes the fuel pump run constantly, even with no key.

 

Thanks for the feedback and information. Did not mention the battery. It is a replacement and is about a year old. It is the TPI, so the fuel pump is in the tank. I check on the possibility that it was running.

 

Had the battery load tested. No problem found. Something must have discharged it. Checked the fuel pump, and the power turns off with the key. Of course it could have been stuck on at one time though. At this point, there is no significant draw on the battery while parked, and it started right up after sitting for six days. I guess we will just wait and see if it happens again.

 

Underhood light work?

They're notorious for not turning back off when the hood is closed.

I leave mine unplugged. In fact, since I NEVER have to work on the car unexpectedly, I don't think I've even had a bulb in it for the last 15 or 20 years or so.

 

Good thought. My car did not come with a light under the hood. Thanks for your efforts. I have not mentioned it, but once I observed the dome lights staying on when the dash switch was off and the doors were closed. They went off when the door was opened and reclosed. Since it is a grounded circuit, there may be an intermittent short in the wiring or door switch somewhere.

 

Found it, I think? The driver's door switch appears to be the problem, as it was making contact at times while the door was closed. Changed out the switch, and now will have to wait and see... Once the switch was removed we found that it is cracked and bent inside of the door post causing it to short on the body.

 

It also depends on how long you drive the car once week. To fully charge the battery after starting the car you have to drive 11 miles at 45 miles an hour... Or something along the lines of that.