W202 Interior lights

[babz]

Hi guys, Im wondering if someone could help me figure out what's going on..

I have upgraded the interior dome lights (2 front & 1 rear) from standard bulbs to LED's. they looked great when i installed them! So i also attempted to change the map reading light, but every time i plugged the LED bulb in, it wouldnt light up.It was blowing the bulb itself every time i switched it on.

So, I have decided to leave the lights as they are (no point damaging anything.) Now i have noticed that the lights (which where VERY bright when i installed them) are very dim. and they wont switch on at all when the engine is running.

i dont know where to start troubleshooting. any help is much appreciated

 

[horgantrevor]

led s are polarized and will only work one way they can not be dimmed like the original bulbs


i would check all earths make sure all connection you changed are correct and clean

and the main fuse in in engine bay

if you had a fault before you started you should fix this first

how were you upgrading the light was it just fitting leds

 

[babz]

When i installed the LEDs they worked fine (faded out like the standard bulbs etc. they still fade out now. Only difference today is that they are a little bit dimmer and only work when the engine is switched off. Ive checked all the fuses and they are fine.

 

[babz]

maybe im being a little bit vague about what the problem is.

I installed the LEDs yesterday, just a simple replacement of bulbs - no wiring alterations at all. they worked fine, they were bright and lit up the cabin well.

Today i attempted to replace the map reading light with a replacement LED, but no matter how many times i tried the map reading bulb wouldnt switch on. So i decided to leave it out as on the last attempt it burned out the LED.

Now the main issue. the LEDs i installed for the main dome lights (2 at front & 1 at rear) work as normal when the engine is off. they fade as normal etc issue is they are very dim, not at all like yesterday. But when they key is turned, the LEDS go out instantly (unlike the usual fade out) and dont come on when i flick the switch.

This has also caused the 'failed bulb' light on the dash. ive checked all the exterior lights and all of them are working fine. Ive checked all the fuses and they are all fine too. i dont know what else i could check. hope this has made it a little bit more clearer to what my problem is.

Thanks in advance!

 

[babz]

Any thoughts anybody??

 

[andy27168]

I take it everything was ok before you swapped the lamps, and the bulb failure light was off. Swap them back to the original lamps and make sure everything works as it should.
When you unlock the car the front and rear interior lights should come on even before any door is open, when you switch the ignition on the lights should fade out.

 

[babz]

Yes, everything was fine before the bulbs were replaced. The bulbs came on and went off as normal, as they did when i originally installed the LEDs. Issue now is they come on as normal (fade on when the door is unlocked & before the door itself is open) but VERY dim. And as soon as they key is turned, they go off instantly and they wont come on whilst the key is still turned. I will try putting the old bulbs back in later today and see what results i get.. hopefully the issue will be sorted.

Am i right in thinking that because the LED replacement bulbs still work (all be it a little dim) that all the connections behind the dome light are fine??

 

[babz]

Any more thoughts anyone? would really appreciate the help.

 

[babz]

Bump

 

[andy27168]

What happened when you put the normal lamps back in?

 

[babz]

they didnt work at all, they wouldn't switch on or anything. Ive put the LEDs back in and they still light up but are still dim.

 

[andy27168]

Measure what voltage you have across the terminals of the lamps, I,m thinking you may of done some damage to the control module, LED lamps are not meant to dim, you can buy dimmable LEDs but they are more expensive than normal lamps.
Where you would buy dimmable automotive lamps I don,t know.

 

[babz]

Thanks for all your input andy27168 & horgantrevor. I fiddled around with everything that i could but unfortunately no luck. ive just got back from my local MB breakers and bought myself the whole front dome unit. Connected the wires and hey presto! all is well again. lights are as bright as they used to be and they fade out as normal. The Merc is once again... completely problem free!

Thanks again Gents!