Unpredictable battery drain

I have a 1991 Buick Regal that suffers from an occasional battery drain. I replaced the alternator about a year ago, and the battery is just a few months old.

Still, every once in awhile, when I get in the car, the battery is completely dead. Not only does it refuse to turn over, but it can’t even muster enough power to turn on a light or operate the automatic locks.

The confusing thing is that this happens at unpredictable intervals. I often leave the car alone for a week or so and it starts just fine. Other times, the battery is drained after sitting unused for as little as 24 hours.

It takes a jump just fine and, once I run it for a bit, starts on its own with no trouble at all.

Does anyone have a clue as to what might cause such odd behavior? Thanks in advance.

Your job will be to try and find something in common with the times it kills the battery. You have an intermittent current drain, so you’ll need to find the cause.

Battery dead when it’s parked on a hill? Check for trunk lights staying on. How about glove box lamps? Under-hood lamp? Sometimes brake lamps get stuck on if the brake lamp switch is mis-adjusted.

Do a little investigating, this will probably be an education for you. And it probably won’t be all that hard to find once you start looking.

Every electrical thing in the car can be responsible for your drain. Try pulling fuses when you park it if you can’t find the drain any other way.

When it does this what do you do? Do you need to recharge the battery? Batteries don’t last long under those conditions.

Since you hare not reporting replacing the battery every few weeks, I suspect that it is not getting drained, but rather it is not delivering power. The fact that jumping seems to help is consistent with this guess. That could be nothing more than poor contacts somewhere on a battery cable or a bad battery cable. You can try removing the battery cables (one end of a cable at a time) and cleaning it and reconnecting it.

I am not clear about the history of this. How often is “once in awhile” and when was the first time? How many times since you get the new battery? When did it first happen?

When I find the car dead, I jump-start it. Usually, I use a jump box. Once I do that and let it run for half an hour or so, the battery seems to take a charge and it re-starts just fine.

As for the history, I would say this has been going on for 3-4 months. It started happening once in awhile, so I replaced the battery, which was a bit old anyway. That did it for a while, but then came the intermittent, unpredictable incidents that I described above. I don’t normally use my car on weekdays, and it doesn’t always do this, so I’d say I’ve jumped it 7-8 times since then.

Here’s one possible thing I’ve been thinking of lately. The previous owner of this car had an automatic starter. The wires and such are still in the car, but I’ve never had a remote or anything and never used it.

A few years ago, it started acting up. I first noticed it when I’d open the car door. Sometimes, when the interior light came on, the car would “ding” as if the key was in the ignition, and then start all on its own – the keys were still in my hand! At that point, I could put the keys in the ignition, turn it to the “on” position and drive away. Or I could step on the brake and turn the car off.

This became a problem when the car began starting itself all on its own. My roommates would sometimes wake me up a couple hours after I went to bed to ask me why my car was running. It had started itself. I eventually discovered there was a switch under the dash to turn off the auto starter, and the problem was solved.

The car hasn’t started itself lately, but maybe there’s a way this is related?

Walmart has battery disconnects that you attach to a battery cable. After installing it, anytime you want to disconnect the battery, you raise the hood and turn the disconnect. The engine cooling fan relay may be intermittently turning the fan on after the engine has cooled. It could continue to run until it drained the battery. As a pre-emptive, change the relay.

I agree with another post. My parents had an Oldmobile with a center console. Sometimes the switch would stick on. The glove compartment light and trunk lights are possiblilities. I had a car where the horn swtich would make contact, the horn would honk, but then the current draw would make the metal strip contacts expand and the horn would then stop. This cycle would repeat itself. You might check to see if the horn is sounding when you aren’t around.

An intermittant problem will be tough to find. In addition to the auto start, glove box etc. possibilities, I have also had problems with the the door knob switch and the leveling mechanism shorting out on my Buicks. I had an intermittant battery drain that I couldn’t figure out and one night I happened to go out to the garage and the interior lights were all on. I disconnected the wire to the door handle and that took care of it. Another I traced to a short in the height control unit so it really can be anything.