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