Hi all, tried to upgrade my wing mirror light to LEDs, fitted them both and working fine until the left hand one went off. Tried the old bulbs which were working fine and none will work in the left hand mirror. Everything else is fine on the other mirror and all the other lights. Any ideas what I've broken or how to fix it?

Have you checked for a blown fuse ?

From what I can work out, the fuse would be the one for all the interior lights and that seems to be fine.

The door lighting is handled by the door control module, which are fused in the rear fuse box.
You'll need to test for power at the door mirror bulb holder. If it's dead, and the rest of the door electrical equipment is working, then it'll be the wiring or door module.
LEDs can do odd things to the output MOSFETs, so I avoid LEDs where normal bulbs were originally fitted. Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.

Turns out the passenger door module fuse is behind my glove box (I guess I have 2013 not 2012 as I had thought), checked the fuse though and it's good so I suppose I'm borrowing (or buying) a volt meter from somebody. Everything else is fine. Will investigate more tomorrow in the daylight. Really appreciate the help though, thank you. I'll keep posting when I figure it out.

Managed to get the light working, after a better look at the connector, it has a little bit of corrosion which I didn't think was too bad but gave it the best clean I could with vinegar and blast with compressed air and after a few wiggles around, I got it to light up. Not convinced it's fixed but we will see how long it lasts. Guessing it's either corroded terminals or possibly a loose wire inside the bulb holder. How simple is this to replace? Snip the wires, connect a new one and all good or is that just wishful thinking?

Thanks for the advice though.