battery drain

[afcb]

hi,

i've gota p reg m3 evo cab which i've just changed the battery 7 days and after 1 day of not driving it - -
the brand new bmw battery (£80) was completely flat.

it has a tracker and a clifford concept 500 alarm.

any ideas on what is causing the battery drain?

ps is it normal for the computer to stay on after you ahve locked the car before turning off?

[M3 Mitch]

In general, you need some sort of ammeter and I'd recommend an inductive digital VOM (has a loop on one end that you can open up and snap around a wire. Failing that you could use an old-fashioned type of ammeter but most of these will require you taking the leads off the battery.

Anyway take a look at the current drain with the car turned off, I don't know the spec for your exact car (is this an E30? We Yanks don't know the tag code used in Britain) Anyway look at the current drain, then pull each fuse in the fuse box (one at a time) till you see a sharp drop in current draw, at this point you have 1) a temporary fix in that you can pull that fuse in the evening and 2) you know which circuit the offending device is on.

An ETM for the car is worth having. In any rate get a manual with a wiring diagram.

"Accept the challenges so you can feel the exhilaration of victory!" (Gen Geo. Patton)

[Tabs]

August 2004 edition of Total BMW magazine has full details of battery drain. It does mention that you need a special battery in a cabriolet, 'as BMW designed the car with the battery acting as a vibration damper to counteract flex in the bodyshell, which means a normal battery won't last more than a few months'.

[afcb]

I bought the new battery for it last week as it does need a special one.

gave up and taken it into a specialist to sort out - cheers for the help

andy