I have a 1984 633csi. Just had the heating core replaced. Car came back with the temp guage not working-- 2 days later the battery was dead. Charged the battery and tightened loose battery cables-- temp guage started working. 2 days later-- dead battery. Charged and tested battery and system-- everything checked out ok. 1 week later-- dead battery. Replaced battery-- temp guage does not work again-- 2 days later the battery is dead again.

Any thoughts???

sounds like a similar problem I'm having with my prizm. the battery is dying for no apparent reason and I'm not sure why.

I need to check some more things on it and if I have any ideas I'll let you know, likewise if you find anything thats easy to check that helps you out let me know

I have the same issue with my 633 (a 1984 as well). The battery is dead after 3 days. I did not find the the problem.

Your help guys will be very usefull.
Thanks

I have a 1984 633csi that needs charging if it sites for more than a couple of weeks.
Again any thoughts appreciated

First of all, if you let a BMW sit for about a week, it will need to have the battery charged up. I have a friend that has a '06 330ci that her battery kept dieing on her. The dealership told her that she has to drive the car for 1/2 an hour once a week or the battery will continue to die. She hasn't had any more problems since. Your battery problem could have to do with a current draw when the car is off. You will need to use a test light connected between the positive battery terminal and the positive cable end. If the light goes on, you have a current draw. Check to see that your glove box, trunk light, interior lights go off when you close the door/ trunk. I hope this gives you a place to start.

First of all, if you let a BMW sit for about a week, it will need to have the battery charged up.

This isn't true at all. I've let my BMW's sit for up to a month (maybe more) at a time and they start right up.

I have a friend that has a '06 330ci that her battery kept dieing on her. The dealership told her that she has to drive the car for 1/2 an hour once a week or the battery will continue to die.

The OP didn't ask about an '06 3 series. They asked about a car that is 22 years older and significantly different. Whatever the dealer told your friend about her car is really not that applicable to this 6 series IMO.

All that said, yes, check your current draw. Also check your alternator (carbon brushes in particular) and maybe grounding points. Stuff like that.