I have a multimeter than can read up to 10A current, so I hooked it between the positive battery cable and the positive battery terminal. With all fuses removed and ignition off, I measured 0 Amp (sort of what you'd expect..)
Installing one fuse after the other (12 total + radio memory), this is what I found. Zero current draw on all fuses except number 9, which drew 15.8 mA. This fuse is marked "Belt interlock unit". I assume this is for the fasten seat belt sign to turn off after the belts are on. But why would it read other than zero? Secondly, the radio memory backup drew 72.8 mA. Does this number sound about right? Add the two and you get about 11.29 hours to draw 1 Ah or about 2.1 Ah per day. If the battery (in good/new condition) can hold about 60 Ah, it would take 14 days to run the battery down 50%. Last time I checked (last fall), the battery would hardly last a week before it wouldn't turn over the starter anymore. The battery is dated yr 2000. I have a gut feeling that (1) fuse 9 should draw zero, (2) the radio memory should draw less and (3) I have a bad battery. What do you think?
P.S. The radio is a CR-712 which came from a late 80's 240.

Kåre

The wire from fuse no. 9 goes up to the ignition. I turned the ignition on and off a couple of times and voila - the current draw dropped to zero. I guess the ignition tumbler needs to be cleaned. As fas as the stereo goes I'll replace it if I cant figure out the high memory current draw. Lastly I will replace the battery too since it's already five years old.

KÃ¥re

G'day all

The belt interlock system draws a fair bit of current, but thats a bit much!
the battery sounds like its getting a bit long in the tooth and wearing out if it was purchased in 2000, still five years is a good amount of life out of a battery. If you live in a hot weather type climate like I do, we usually get about two years max out of a battery in our brick ('89 744GL)no matter how good your charging system is.

Whats the wiring insulation like in your car? It may be chafing or crumbling around the wire and causing a partial short curcuit (where a small amount of current is being "earthed" to the body but is not enough to cause a full blown short curcuit)I discovered this problem in my brick on the wiring harness on the motor that connects to vital things like the computer and the temperature guage and warning lights.

The backup wire should draw less than that, maybe 0.56mA

To expand on this good reply, it's likely you have water in the wiring. Virtually impossible to get out, and even if you do the wire wil already be oxidised and should rather be replaced.

Depending on the design of the radio, the backup current should be in the order of 10 to 50 uA, definately less than 1mA. The seat belt relay should be electrically disconnected when the ignition is off, and thus draw no current. But it might have a switched input and an unswitched output, so perhaps water at the input could cause a power drain on the output (if that makes sense to you).

On my 240 the fuel pump relay and driving lights relay was fitted hanging down, and got filled up with water. Amazing how long the car still works with water in there! Anyway, water can cause nasty problems and it is best to replace rather than repair. Have fun...

I live outside Phoenix, Arizona which would probably be considered relatively cool compared to some parts of Australia (although we've been hovering around 115 F for a while now). I agree with you that the battery is likely shot.

Kåre

Get a deep-cycle battery with starting ability and you won't have to replace it for 10 years or better. The deep-cycle units have much heavier plates in them and will not sulfide-up nearly as quickly.

--
Mike!

And it has cleaner acid.