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Battery problem

2007 Monte Carlo has dead battery after a couple of days sitting. We’ve un connected alarm, etc still dies its a new battery. They say I don’t drive it enough.

Did you replace battery because of this? Did you drive the car around to fully charge the battery before you parked it? How much DO you drive? We need a little more info so we can help you.

You may have the right idea, if something is draining the battery, it could be anything connected to the electrical system. Remove the red battery cable and attach an ammeter between it and the battery. Note the current draw, it should be 20 milliamps or so. If it is higher than, say 200 milliamps, pull fuses one by one until the drain drops, that is the culprit.

If you have NO idea what I just wrote, take it to a good mechanic and be prepared to pay him for the time it takes him to just find the problem as well as repair it. Electrical gremlins can be a bear to find and fix.

Thanks for your great answer. We’ve tried new batteries. The mechanic said it was the alarm but it died with no alarm connected. I will try driving it more but I have a car in the garage I hardly drive but it doesn’t die for months. Now I start it every other day. A friend and I may do the ammeter test you described. Any body else have any idea what’s draining this battery. The car has On Star, alarm, computer. I asked On Star to quit running its diagnostics but car still dies after a few days or when it gets cold outside.

mine does the exact same. when its cold even quicker. I think I have faulty diodes in the alternator that allow the charge to leak away. if this is the problem, the diodes may be replaced or the alternator may be replaced completely. there is a whole thread about my prob here somewhere. I ll check for the title and post it.

the title is “diode rectifier problem?” and I bumped it up to the first page for you

read the whole thing as there is some debate before its fully hashed out

@Cat Marcy, I think the mechanic pointed to the alarm because it is the most obvious. Aftermarket products don’t seem to worry about how much current they draw. As you found out, that wasn’t it. @wesw may be right, it could be a diode in the alternator, too. After running the “pull a fuse” and check the current test and still not finding anything, THAT might be the problem.

Be sure to check the battery for a full charge though. A friend’s seldom used Toyota 4 Runner kept running its new battery down until it wouldn’ start. We put a trickle charger on it for a day to bring the battery up to full charge. He never had a problem after that. He drove it just enough to recover the charge but not enough to bring a new, but somewhat undercharged battery, to a fully charged state.