i have a 91 740 wagon that dies after about 3 days if i don't drive it at all. something is draining my battery and i can't figure out what it is. i bought a brand new battery at sears back in september and it still dies after a few days of non use. i turn off everything before i turn the engine off including all the overhead lights, heater, radio, etc.. any suggestions as to where i should look next?

Hi:

Remove the relay for the Automatic Locking system and see if the problem goes away. That's where my problem was. A door locking motor was hanging up causing a similar problem.

The system will run ok with the relay removed. You just won't have an automatic locking system.

Good luck

i still haven't figured it out, but in the meantime i put one of those battery disconnect knobs on it so i won't have to worry about it draining in the meantime.

I have an 87 740 GLE and mine was doing just about the same thing. so i went and started looking for things that could be my problem when i found that the ground wire coming off the alternator was not conneceted anymore. so i would look at your alternator first.

Do a search here for "battery drain" and you should fine some information. Not sure if anything is in FAQ for this one.

Essentially you take a multimeter and look for current draw. I can't recall exactly but when I tested my 740 it had about 10mA draw. The clock will take some power.

Remove one of the terminals (I don't recall which is best) and check draw between the two. If you find a significant draw >200mA then remove each fuse one at a time and recheck.

Are you sure alternator is properly charging?
--
Norm Cook; Vancouver BC; 1989 745T 210,000KM