03-04 Impala, 3.4

[MNice]

Not mine, helping a friend...Intermittent problem, aren't those the best

Problem: Every so often the car will drain battery dead... not all the time, once every couple of weeks.

Items verified. Battery OK, alternator OK. connections ok. Normal fuses verified not drawing when shut off.

My guess. I'm guessing these have some timed relays when the key shuts off that is not operating properly, (like lights staying on for 15-30 seconds) Think I'm on track, or wandering aimlessly through electrical nightmare??

[delcecchi]

When this used to come up on "car talk" it was typically one of the lights staying on, trunk, under hood, glove compartment.

Like how do you tell if the trunk light really goes off when you close it?

[flipper]

Quote:

Like how do you tell if the trunk light really goes off when you close it?

Just get in the trunk and then pull it shut.

OR

Find the switch that shuts the light off when the trunk is closed and check it without shutting the trunk.

[Jeremy airjer W]

A little more info would help.

Is this a daily driver? Does the battery go dead overnight? Does the car sit for a couple of days and then the battery goes dead?

[MNice]

Found out more info.. It's a 02. Daily driver, 25 miles one way. It's gone dead overnight and even while at work in a 8 or 9 hour day. I'm going to work on it this weekend. I plan to disconnect the negative on the battery, and see what we have for parasitic amperage. Maybe we'll get lucky and find a big draw, then hopefully we can isolate it.

Thanks to all..

[Jeremy airjer W]

If it goes dead overnight it should be a pretty healthy draw. Anything over .050 amps is to much.

I would also suggest swinging buy your local library and print off the power distribution diagrams. Most public libraries offer free all data and only charge for the print outs. Once you have isolated the circuit buy pulling fuses one at a time, the wiring diagrams will show you what is on that circuit. You can then further isolate the draw by unplugging individual components.

I usually start with the normal suspects by pulling Radio, courtesy lights, heated seats, power/heated mirrors, and BCM fuses.

Also note that once you hook up your amp meter in series with the battery it may take 20-30 minutes for everything to power down. Be patient. If you see more than .300 amps what for a bit, it will likely drop to somewhere around .150 amps.

How old is the battery? Might not be a bad idea to have it tested. Most auto parts stores will do this for free.