I’ve had LED bulbs in my dome light for several years. Just the other day I noticed when both doors are closed, the left bulb goes out completely, but right side bulb remains faintly illuminated. This is of course with the dome switch in the middle (doors) position. In the off position, both bulbs are completely dark.

I briefly fiddled with the switches on both door sills and they seem to be operating smoothly (causing no flickering in their travel). I haven’t looked beyond that… any thoughts on where to start? Bad ground connection somewhere?

 

Normal with cheap led bulbs.

There is a tiny amount of current flowing through incandescent bulbs, but not enough to make any light. Smart leds have circuitry to prevent illumination below a set threshold. Cheap ones don't. Yet bc led so efficient, they can illuminate with that small amount of voltage.

Either live with it or buy better led bulbs.

 

Problem, err… solved?.

Thanks, but they’re not cheap LED’s. I’ve been running them for about 7 years and this is a completely new issue.

So I dove into it today and here’s what I found… When swapping bulbs, the issue persisted on the right side… it didn’t follow the bulb. In the middle switch position with the doors closed, I was reading ~12v to the right bulb only. The left bulb didn’t have that voltage.

I removed the left mounting screw, which provides ground for the “always on” circuit (right position). That stopped the unwanted voltage in the middle (doors closed) position. With that ground removed, the middle (doors open) position still illuminates, as ground for that circuit is provided through the wiring harness.

That made me suspect perhaps a short in the dome light wiring or switch. I pulled the dome light and took apart the switch mechanism. I found nothing out of the ordinary. No exposed wires, no debris inside the switch… the contacts were still perfectly clean. I put it back together, tested the switch and got continuity at the appropriate contacts.

That’s when I shrugged, put it all back together and found that whatever I did, I solved the problem

 

Keep an eye on it and be prepared to have to jump start the car at some point. A Battery Tender will help to keep the battery charged, but if you take it anywhere for an extended period of time, be sure to have a jumper or cables handy.

Or, buy new bulbs. After 7 years, its probably about time anyway and those bulbs owe you nothing at this point!

 

Nope. He is actually using no more battery juice now with led lighting up than if he had incandescent that produce no light.

He literally has voltage at the bulb. That means current available to flow. But just not much current. Not enough to light led normally. But if it were incandescent, current would also flow, just not enough to produce enough heat to create any light.

Mine is doing same thing, interestingly, sa.e side, right. Healthy battery, I can park for weeks no apparent battery degradation.

 

Unfortunately, the right bulb illuminated again during the next drive. I tried further to find fault with the circuits, but couldn’t. I agree with Car Analogy that the unwanted voltage will pass through LEDs and incandescents alike, but such a low current that I don’t fear the battery draining. The faint illumination is enough to be a visual distraction at night, so I ordered some new bulbs that I hope will suppress the low current. I’ll update later with results.

 

For the map light, I ordered Diode Dynamics HP6 in "Warm White” (3000K). While I was there, I also got a 3000K for the trunk and a 4000K for the rear license plate. My prior LEDs were much whiter (perhaps 6000K). I find the interior is much more inviting under the warmer color temp.

So far I’ve only taken a short drive, but no issues with illuminating in the off position

 

You're going to get variations in LED bulbs like that - Some seem to still work with the very small current leak; others don't. I personally run all Philips LEDs on my car, and I mean ALL (blinkers, parking lights, hi-beams, interior etc etc etc) Never had an issue with the partial illumination. Personally, I prefer more reputable brands that have been in the game for a while. DD and Morimoto also come to mind, but damn if they aint cheap. I find the Philips ones very reasonable in comparison. Glad ya got it sorted - that would've bugged the hell outta me.