Battery Drains Without Key in Ignition

Hello, the battery on my 4.2 liter inline 6 2008 chevy trailblazer is draining without the key in the ignition. I have checked the alternator, fuses, and starter with no luck. Any idea what might be causing this problem?

This is normal for modern cars. It keeps some of the computer stuff running full time. The question is the degree. How old is the battery. If it is original equipment, it is time for a new battery on a 2008 model.

I’ll let someone with more details help you out with checking to see if it is just old or how to test it.

You should have your battery & charging system checked. Most auto parts stores will do this for free. You also should clean you battery / cable terminals & make sure they are good & tight. Chances are your battery is just at the end of the line.

If all of that checks out then it needs to be checked for a parasitic draw on the battery - something that is pulling too much power with the engine off. A basic way to do that involves hooking up and ammeter and if the draw is more than about 50 milliamps or so you start pulling fuses until the draw drops.

I hooked up the ammeter in series between the negative battery terminal and disconnected battery lead, and with the ammeter set a 500ma, the needle was pegged out. The draw is better than 500 and less than 1000. The battery should not be the problem since there is a draw coming from it. I pulled all the fuses, disconnected the alternator, and disconnected the started solenoid without the needle going down.

If you pulled all of the fuses w/o it going down… Are you SURE you got all the fuses…I believe you have an internal and external fuse box on that vehicle. If you got all of the fuses out then the only two BIG items that are hooked up that are common causes of Batt drain are the alternator and the starter.

Continue your Meter test and disconnect the hot wire going to the back of your alternator and see what you get…if nothing…then disconnect the hot to the starter. Methinks you will find it on one of these two items…Alternator being highest on my list followed by the starter…Let us know what you get.

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Thanks for the help everyone! I’ve pulled all fuses under the hood and under the seat inside the car. Tomorrow I’m going to do it all over again after allowing about thirty minutes from the time I opened the door. Wish me luck!

Make sure the battery is fully charged or this whole thing doesn’t work right.

I also just have to say it - make sure that the underhood light isn’t on. I can’t imagine that it is. I don’t think I’ve ever seen one of those with a good bulb in it.

I had a Subaru with lo-jack, aftermarket alarm sys., and satellite radio. If I didn’t run it every 3 or 4 days in winter or about 7 days in summer it would not start. Dead battery

So teward what was the issue???

You evidently have a trailblazer with a similar problem. Are there things that are not working as they should? That would be a good starting point. Hoping for a response on a post this old is probably not going to happen.