Electrical problem on my car. Can anyone help?

[Pitbull]

Just bought a 1400 Rover 200. T Reg. I think it's the Honda engine that has been fitted. When I first bought it, I jetwashed the engine bay. I have done this on every car I have ever bought and it's never caused a problem.

The car ran a bit rough for a few days, but after it dried it ran beautifully for well over a week. One morning I got up and the battery was flat. I jump started it and it was ok. The next time I used it, it was flat again.

I've put a tester across it and it's drawing 3 amps with everything turned off, including the factory fitted imobiliser. Then evey fuse and relay was pulled in turn and nothing changed. It's only a 20 amp battery (which was fitted Feb), so it runs flat within 7 hours.
I have cleaned up all the earth straps and cleaned and tested the starter motor. I also swapped the batteries over with my Audi (55amp) overnight. The battery started my Audi in the morning, but the Rover had flattened the Audi battery

Are there any petrolheads, electricians, car mechanics or logically thinking people out there who can help with the problem.

Please, no one suggest a garage. I haven't got a pot to do anything in !!!

I really need this problem sorted as it's my wife's car and my ears can't take any more of her chewing.

[poyks]

Have you tried isolating individual electrical systems such as ignition, starter solenoid etc, then doing the current test again? It almost sounds like a problem with the ignition key switch.

Also try putting an ohm-meter across the disconnected battery terminals to check the resistance.

[Pitbull]

Thanks for the advice Poyks. The only thing I didn't get round to testing was the alternator. That was a good 3 or 4 hour job that I was avoiding till I tested all the easy stuff.

I did find the problem in the end. It would have been really easy just to phone my sister in law who we bought the car from, but she has been in the States for a month.

She eventually told us that if you don't SLAM the boot, the light won't turn off. I removed the bulb and waited 24 hours.
Started first time.

How can something so small cause a battery to run flat overnight?

Problem sorted now so I'm happy.