Been playing with the SE as the weather was nice, I've run out of things to do on mine and having got the engine running nicely without peeing fuel out of the injector seals and the passenger central locking working again, I decided to check the current drain. The battery on it is completely FUBAR'ed and doesn't want to take or hold a charge so I just hang jump leads on it and use my spare battery to power it. The battery was a decent one when I put it on so aren't sure why it has now died but hung my meter on it to check the current drain. Closed everything and locked the car, current drawn was 900mA, after 30 seconds it dropped to 600mA and after 2 minutes when the BeCM went to sleep, it dropped to 100mA and stayed there. Left it for over half an hour and it was still drawing 100mA. So what is dissipating 1.2W permanently? Further investigation required but it seems to be too low for anything meaningful but high enough to drain the battery when left for a long time. Draining the battery to completely flat and leaving it like that is probably what killed it in the first place too.

And yes, I did disconnect the battery on it and was checking from my external battery only. Didn't to start with then realised I was measuring the current my decent battery was trying to put into the duff one as well as what the car was drawing.

Pull fuses and see what causes it to drop... is it factory stereo or aftermarket?

Does it have a tow hitch and has it been wired correctly mine wasn't!

Disconnecting the stereo and pulling fuses was going to be the next step. Stereo is an aftermarket Sony which used to have a Parrot bluetooth unit attached to it. That was wired the wrong way round so was permanently powered but I'd assumed since I took that out it should have been OK. Parrot unit had in and out DIN plugs and was just plumbed in between the car and the stereo but had the permanent and ignition switched feeds reversed.

Does it have a tow hitch? Of course it does, what's the point of a P38 without one? Although that is wired correctly or at least as correctly as needed for the trailer lights to work.

If it has had a 12S socket wired in with a voltage sensing relay box, it could be energising its relay(s) constantly causing your draw. Mine had one fitted behind the tail light assembly on the passenger side, and it had gotten wet at some point. Lots of corrosion and it was clicking on and off at random.

No, standard 7 pin trailer socket, so no voltage sensing stuff anywhere. LPG system has been removed too as it's going to be sold on eBay as a spares or repair job and the LPG system is probably worth as much as the whole car will fetch. It's actually pretty good, has quite a few new bits on it but has a cracked windscreen and my trade policy doesn't cover windscreens and I don't fancy spending £525 for a new heated windscreen. We will be moving house in a couple of months too so shifting 2 P38's, Dina's Merc, my Maserati and company van as well as the contents of the house means at least the SE (and possibly the Masser) has to go.

In case anyone was wondering, I lent the Ascot to my boss before Christmas as his 55 plate Disco had died and he had no wheels. His Disco is still dead and he's running around in the Ascot although he has asked how much I want for it. Selling a 21 year old P38 to my boss could be either a good move or a severe career limiting move (but as I retire in a couple of years my career is unlikely to progress anyway).

Well the later P38s had battery backed sounders, quite possibly from BMW so it sounds like a good one to try!

Good point, no idea if it is a battery backed sounder or not but I know it works (managed to set it off twice while mucking around at the weekend). That's another thing to disconnect while the meter is measuring the current draw.

If it sounds like a siren rather than a horn, then its probably a battery backed sounder. Sounds feasible it could be trying to charge batteries that are crapping out.