Major electrical problem - any ideas?

Hey gang.

I've been having some serious electrical problems with my S12. -Something- keeps draining the battery. I don't know what it is, I've tried everything I can think of. One of the headlight relays was f**ked, so the headlights kept switching themselves on all the time, and of course that drained the battery, but I fixed that. The alternator's fine, the headlights aren't drawing current any more (unless I tell them to, i.e they're a-OK again), I haven't added any stereo components (yet) like amplifiers or capacitors which might get a bit current-hungry, all the lights seem to work...what the hell could it possibly be?

do you have a multi meter or volt meter? check the voltage of the battery with the car running, then check it with the car off. have you replaced the battery since the light voltage problem? im thinking you may have a bad cell in your battery, or your battery does not hold a charge.

Check your brake lights.....have you noticed if they stay on all the time?
This happened to me and kept draining my battery, and it took me several days to figure out this was the culpret.
Come to find out....it was some little safety bump stop at the top of the brake pedal arm that had broke off, that was causing the brake lights to stay on all the time.
Might be worth a looksey.

slosc2: thanks for the suggestion but it's definitely not the battery. It's a brand new battery and since this problem came up about a week ago I've spent two days running it in my N13 Pulsar (with its big-ass stereo and all) with zero problems.

Keith: I hope it's not the brake lights! I had another problem with them where the lights weren't coming on when I braked. That was easy to fix, though: the globes had fallen out of their mountings! I'll have to jump start the car to check whether the brake lights are coming on without me wanting them to, so I'll do that tonight - the car is about a fifteen minute drive from where I am, in a storage yard, purely because I have no space where I'm currently living for it. Cheers for the suggestion too.