Battery drains in my 1984 BMW 318i

If the alternator is charging the battery it will not be the fuse. The alternator would simply stop working if the fuse has blown.
If the battery isn't holding charge you might have a power drain somewhere in the vehicle. Something in the electrics may not be turning off correctly and draining the battery. Do you have any warning lights on the dash? Have you access to an OBD2 scanner to check for any Trouble Codes?
If it is a power drain the simplest fix is to get a good Auto Electrician to check the vehicle. Finding a power drain or an electrical short can be a real pain in the tail bone job because there is so much electronics on a car. Paying an expert to do it is a lot quicker and easier as they have the right tools to do it.

HELP 2000 Z3 Battery Drain - Bimmerfest - BMW Forums

www.bimmerfest.com > ... > Z Series > E36/7 Z3 (1996-2002)

Feb 18, 2007 - 7 posts - ‎6 authors
HELP 2000 Z3 Battery Drain E36/7 Z3 (1996-2002) ... Something is draining the battery. ... Posts: 55. Mein Auto: 2000 BMW Z3 2.8 Roadster. z3 1.9 battery drain (fuse 31)
6 posts
Apr 9, 2013
Intermittent car battery drain problem NEED HELP
25 posts
Jan 29, 2013
Mysterious Battery Drain
25 posts
Feb 23, 2008
Battery drain....after 2 days sitting dead...
25 posts
Mar 28, 2006
More results from www.bimmerfest.com

misfire is due to a faulty coilpack or bad wire or connection. the drain on your system is another issue. youll have to chase it down with a voltmeter

If the battery is ok and the alternator is ok u probably have a battery drain on the vehicle to test this u will have to put a mulimeter inline with the positive battery lead and check for amp draw. When checking this the ign needs to be switched off 0.05 amps is the most u should read if it's more than this pull out the fuses from the fuse box untill it drops this is how u find out what circuit the drain is on

it seems like something is draining your battery while the car sits overnight. causing the battery to get weaker and weaker putting stress on the alternator making it fail prematurely. the dealership will do a paracidic drain test where they'll find out what is draining your battery while your car sits overnight. it could be a bad module somewhere that's staying on when it shouldn't be.

Need to test the battery ,and the alternator for a discharge .Was a new alternator used or a reconditioned one ?? ignore the lights for the minute because they sound as though the regulator is working ,iam more concerned about the diode pack in the alternator,hence was it a new one or a recon or one from a scrappers

any battery that sits has the potential to drain. when storing your vehicle, remove the negative terminal from the battery. this should aid in keeping the battery alive. excellent vehicle. enjoy driving it. by the way, make sure you get the proper battery for either the L6 or the V12 motor. it makes a world of difference in the long run.

Checkyour alterntor, the battery light goes on  if the alternator is going bad. GOOD LUCK!

a common fault for flat batteries reguardless of car band is the boot light.check that the boot light is turning off when the boot lid is closed.

Check out the the final stage resistor, know weak point that when it fails it leaves the little fan (which I think draws sample air into the themomostat for the ac system) this will drain the battery.