My 1997 BMW 318is started making a whirring noise that varies with engine speed, and an electrical burning smell after driving, and the battery goes flat very quickly.
I measured the current draw with everything off and no key in, and it is constantly around 3.5 Amps.
I tried removing every fuse and relay from under the bonnet, then every fuse, module and relay I could find inside the car. Nothing stopped the current draw.
I then removed the power lead to the starter motor/alternator/unloader relay and the current draw stopped. (There is not good access to the starter itself so I wasn't able to just disconnect the starter on its own.)
My theory is the starter solenoid is always energised so is drawing the current, and that could cause the whirring noise as the starter might be permanently spinning with the engine. The burning smell could be because the starter is not designed to spin at driving engine speeds.
Is this likely? What would cause the solenoid to be permanently energised even with no key in the car? Could it be the starter motor itself?
Someone suggested the unloader relay but I have no idea where it is... I may have already disconnected it. Could it be the cause?
Would it be safe to drive the car 5 minutes to a garage if I keep the engine speeds as low as possible?
Update: I was able to disconnect the big red wire on the back of the alternator only, and the current draw stopped. Does this mean the alternator is the cause?