The battery in my 1996 850 wagon has gone dead while the car sat for a week on two occasions - once 6 months ago, and once recently. Each time, I jump-started the car and it has started and run without a problem afterwards, as long as I use it on a regular basis.

Does anyone have any advice about whether this is a short or a battery that won't hold a charge? The battery is a two-year-old Interstate, so it *should* be OK... The charging system seems fine, giving 13.6 V when the engine is on. I checked for stray lamps that might be on, and didn't find any.. (might there be a tricky one?). One last test I did was to check the quiescent draw on the battery with everything off - removed the positive terminal and attached an ammeter between the battery post and the terminal. I measured about 150 milliamps. I know there is always some draw because of anti-theft, keyless entry, and various other systems, but I have no idea whether this is too much or about right. Can anyone give me a ballpark?

Any advice or experience with this problem would be greatly appreciated!

Thanks to all - problem is now fixed. It was that pesky glovebox light. I pulled the bulb and now the draw is down to 25 mA. Seems to me the problem was the bracket holding the switch, not the door. The bracket is very squishy, and doesn't hold the switch far enough out. But who needs a glovebox light anyway?

The ball park you are looking for is in the area of 25 milliamps. The old 240's routinely would draw less that 10, as the cars became more sophisticated we saw higher and higher parasitic load values. That number really jumped when we got to the 850's. It used to be you could back feed the system with a 9 volt battery wired into the cigarette lighter while you changed the cars battery and you would not loose radio codes or presets. When the 850 came along that went out the window as it will suck a 9 volt inside out before you can change out the battery. However if you can keep the load down to 25 milliamps or less and you do not leave the vehicle parked for weeks on end then you should be ok. Like the other reply said, take a look at your glove box light first and if that does not work then like the other guy said, start pulling your fuses one at a time and when you get to the one that drops the meter down to an acceptable level then go ahead and trouble shoot that circuit.

I can get you the actual number on Monday...allowed draw...

but...you said you checked lamps...more often than not, the problem is the glove box light. The "door" just gets a little loose, and hangs "just a bit" open, allowing the light to stay on. I'd love for someone to tell me how they've tightened it if they have...we just pull the bulb.

Chris

Put an ampmeter in series with the positive post and the positive batt cable. Start removing fuses ine at a time until the drain goes away. When you find one that significantly drops the current drain, that will be the culprit. Then trouble shoot that system.

Yep,
I'd go with the last tip too. If you really want to figure it out, you just going to have to get your little ohmeter tool one nice day, lay it all out and one-by one, start picking circuits until you find a significant spike in one that shows a large difference. This way, you dont have to keep jumping your battery. Your neighbors will frown the more you do this jump thing and gives crooks an impression you are always away. Bottom line is this shouldn't happen even after a month - trickle current or not. We are talking of a big battery probably bigger and much heavier than your head not a little 9V cartridge. I came back after a month of WINTER and started up my bimmer with no prob. Just crank, a little sputter due to the fuel rushing through the dried chambers and the pistons were firing!
So you need to fix things. good luck though