dome light 5V when off??

tzepp27 · 11-10-2009, 04:39 PM

i replaced the stock brown dome light with a LED panel light it looks great! but even when the swicth is off the LED lights up VERY dim i check into it and theres 5 volts still going to it? anyone eles have this problem??

**Wdhitch** · 11-10-2009, 04:49 PM

I don't see it as a problem but yes... there's partial voltage going to the light.

tzepp27 · 11-10-2009, 04:54 PM

can anyone think of any reason why?

jetfuel · 11-10-2009, 05:20 PM

..the dimming of the dome light is controlled thru the computer by varying the ground...check the ground and see if it is removed when it fades to black...

jetfuel...

BigWarpGuy · 11-10-2009, 05:58 PM

I have an LED in the dome light. It is very dim and does not bother me. If you flip the switch to off, it goes off all together. I leave it on auto. It does not bother me.

John_H · 11-10-2009, 06:53 PM

I made measurements a while back. Yes there's a slight voltage (or perhaps "current" is a more appropriate description). I don't know why they'd design a circuit that doesn't present a real open circuit. It's not a problem for incandescents but it's a problem for some LEDs. A 10kohm resistor in parallel with the LED should help swamp out the current.

I originally though the remnant power was from an analog ramp to brighten and dim the bulb but it turns out they ue "pulse width modulation" to make the bulb appear as a varying brightness with full-on and full-off power levels.

trekguy · 11-10-2009, 07:05 PM

You just discoverd a way to have ambient cabin lighting in your smart... truly just like a Mercedes-Benz S-Class.

vwaudimb · 11-10-2009, 09:54 PM

Quote:

Originally Posted by trekguy

You just discoverd a way to have ambient cabin lighting in your smart... truly just like a Mercedes-Benz S-Class.

i agree with you, i was trying to find a led ambient light like my c-class but this solves the project