I thought I'd revisit this thread with a possible "gotcha" based on a recent (somewhat scary!) personal experience.
I replaced my two interior front door lights (the ones in the armrests with the red lenses) with 28mm Yorkim De3175 LED "festoon" bulbs.
These worked great at first. I polished off all the scratches on the red lenses, and enjoyed my new brighter bulbs, happy that they'd no longer be likely to drain my battery while camping.
Then, several months later, on my birthday of all days, I went to start up my van (usually starts up right off, but it'd been a while since our last trip). I cranked it several times, no luck. Then I smelled something. Then I saw smoke.
When I flung open the passenger door to investigate (thought it was from the engine at first!), I saw a very tiny fire burning brightly inside the passenger armrest, with an ever-widening opening in the red lens covering what had been the little door light.
I put the fire out quickly, but the smell was awful, and has taken some time to air out! The plastic lamp housing inside the armrest had melted around the wiring harness that connects there. What had once been my LED lamp came out in almost unrecognizable chunks.
My father's an electrical engineer, so we did some troubleshooting. There appears to be nothing amiss with the battery setup or wiring in the van. He believes there's a design flaw with these LED "festoon" bulbs though: the metal heat sink that spans them. He thinks that heat warped it slightly, such that the metal heat sink contacted both sides, shorting out the circuit there. No fuse blew, instead... well, fire and smoke!
Here's a photo of how my red lens looked afterwards, rather sorry for itself (the melted white lamp housing looked like an amorphous blob, not pictured). Also in the photo, the other still-good-but-now-uninstalled driver side door's LED lamp, which may possibly be a design to avoid? Thinking of doing something custom with a clear lens, so that the LED can be smaller/less powerful, with no need for a heat sink on it!
The odd thing is, I didn't even think that the front passenger door was ajar when I was starting it up, so it's strange there was electrical current going to that lamp at all (I don't think those red lamps come on when you go to start up the van... though I can't check now, having so hastily uninstalled the driver's side door lamp to prevent further fiery issues). The battery had almost enough charge, but not quite, to start the vehicle.
