740 - slowly draining battery?
 

Hi

I've noticed that my new (to me!) 740 can take a few seconds to fire up sometimes, first thing in the morning or after work - i.e. when it's sat for a good number of hours.

Watching my dash voltmeter, when the car is running it looks like about 14v, which suggests to me the alternator is fine. When the car has been running for a while but switched off, key in pos. 2 so that all the gauges are on, it looks about 12v. But when I got in it this morning, before cranking it was a little above the red 10v area, definitely less than 'car off but recently driven so fully charged'.

I figure I've either got a drain somewhere or my battery is duff. The latter can be easily fixed with a replacement, but if there's a drain somewhere that's still going to be an issue.

Is there a good way to find out if there's an electrical drain somewhere? Any likely candidates? Not quite sure how to tackle this. I guess I could measure current flow when the car is off, but there should be a current flow normally, yes? Stereo draws something, clock draws something. Any help/experiences appreciated. Thanks

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'89 740 GL wagon

Do the simple thing first. Have a load test done on the battery to rule it out. Assuming it's good (probably is not and you can stop here) the simple man's way to isolate a draw is to remove one fuse at a time and take readings across the battery until you get a different reading. Yes, there is always a voltage draw for the items you mentioned plus memory for the ecu. Still, the car should be able to sit up well over a month w/o issue. Have the battery checked soon...a bad battery will burn up an alternator faster than one would like.

Thanks, Swift, that makes sense. I'll get a load test done and then see where I am.

Cheers

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'89 740 GL wagon

Popped the hood tonight ahead of going for a load test and the sticker on the top of the battery says 3-05, so at over six years old I'm thinking it's about time to retire this battery. I'll do that first and then see how everything's behaving.

Note to self - always do the reeeeeaaaaaly simple things first...

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'89 740 GL wagon

Hm my battery/meter and stuff is doing that too. Ill have to check into that as well. xD