Proper way is to get a decent amp clamp multimeter, lift bonnet, put a weight on the bonnet alarm switch, lock car, leave 15 minutes and then see what the drain is with the clamp around the battery earth leads (or positive ones). It should settle to 60-80mA. If not start pulling fuses from all three fuse boxes until it does and note which fuse fixed it.
If you don't have that kit and do have a lot of of time you can achieve the same by pulling all the fuses and replacing them one by one until the problem re-occurs. There are some fused circuits more likely than others, I would try the engine room small fuse box with the large fuses first, AKA 'first auxilliary fuse box' . Also have a search on this forum for other suspect fused circuits.
You may then get to where I am - my new battey will drain to about 50% (12.1V) if I leave the car a week between short journeys. The drain is small but even at 80ma draw a 66a/h battery would be completely flat in 1 month. I got bored tracking it down last time I looked it still seemed to be in the wires to the powersounder, which was the first thing I removed. Maybe it is just me not using the car enough. Come winter I'll have another go.
Author
Topic: why is my battery still going flat ? (Read 1607 times)