Driver's headlight on by itself

[Honolulu]

Neighbor called tonight after a heavy rain... I left the front windows open 1.5" on my 2001 'vert... car is pretty wet inside, will mop it up tomorrow.

But the strange thing (which my excellent neighbor called about) was that the driver's side headlight (only) came on by itself. No other lights came on. Light switch is off. No CEL. Car starts right up, both headlights work on high and low beam as do the driving lights, but the driver's side stays on after shutdown.

I can only think that the headlight switch got wet and will try to dry it out tomorrow. For now I've disconnected the battery and come here to post this strange event.

Anyone have this happen to them? Cause? Solution? TIA!

[X3456]

I was going to suggest disconnecting the battery...charge it up too.
Yep, there have been reports of during rain storms windows going down , it happened to me a couple of times.
One headlight on after storm... sounds like something that would happen.
Best to remember...The BMW is nothing more then a computer on wheels.
Keep that battery fully charged every Friday or so, i got battery on the smart charger especially before and after long travel trips. Just the nature of the beast.

Sent from my REVVL V+ 5G using Tapatalk

[Honolulu]

Thanks... I think. My current theory is that if the headlights are each controlled by a relay, if the left side relay is stuck in the closed position (as could happen during a low voltage event, this was a problem on older BMW K-series cycles) then the light would remain on. This presupposes that the relay is powered when the ignition switch is off, which is easy enough to check. Oh for a proper ETM, then I'd have wiring diagrams in hand.

Well, the rain has (mostly) stopped and it's E46 whack-a-mole time. AGAIN. This car has only 32,000 miles but it's been one d*mn thing after another.

[Honolulu]

NEWS... apparently the Bentley E46 manual is online at http://bmw.n84.eu/e46/E46_Bentley_Service_Manual.pdf

Thought all the Bentley manuals were copyrighted and nowhere available online... now I have enough to really get myself in trouble. Sadly, there are no wiring diagrams, those would be in the ETM and if I can find that, it will be a sunny day.

[E39 Newbie]

Best guess is that your headlight switch, which is attached to the Light Control Module, got wet and flaked out. Weird things happen when that module has problems.

My E39 LKM (under the RH kick panel) got wet because the PO cheaped out on a windshield reseal and the module had gotten wet a time or three and corroded. I had similar weird things. One headlight on. Or one halo light on. Eventually the turn signals went on and couldn't be turned off. Turned out to be bad LKM.