[Dying Battery Issue: Tracing Parasitic Draw?]

I had the same problem, just fixed it yesterday! 

I used a multimeter with a milliamp scale between the negative terminal and the chassis with everything switched off.

There was a 74.2 milliamp drain. (it should be 50 or less) 

The next step is to remove (and replace ) the fuses one at a time, when you've removed the fuse that is powering the circuit responsible for the parasitic drain the milliamp reading will drop.

In my case the circuit was fuse 21. The interior lights, including the luggage compartment and the glove box. The rechargeable flashlight, the stereo system, the clock and OBC.

Anyway it turned out to be a "sticky hazard warning light switch, as per andyhunly above! This is one of the few circuits that stays live when the car is locked up.

After I depressed the hazard switch on and off several times to free it up (it now works properly) the drain fell from 74.2 to 14.2 ma - well within acceptable limits.

If the SI batteries are faulty / worn out they can also be a common source of parasitic drain. bavrest.com offer a great service for refurbished  instruments and SI boards

[Newbie introducyion]

Hi I'm new to the site. Have been an E30 owner/mechanic since 2000 when I bought a diamond schwartz 320i SE 2 door. Since then I've done everything including a re-shell. It is off the road waiting for it's 30th birthday when I'll be able to tax and insure it as a classic. Nice to be with you and I hope I can help with some questions in the future.