W124 unknown bulb out?
 

The exterior lamp failure warning light is on in the dash in our 91 300TE. The strange thing is that I cannot figure out which light is out. The headlights, parking lights, license plate and rear lights are all on. To complicate the situation - this warning light is on as soon as I start the car, without turning the lights on.

Not familiar with what would cause this...anyone else have seen this?

Dome light? It might still be on by the time you start the car. Not sure how long the time delay is, but I think long enough to put on the seatbelt and give the key a twist. Slide the button to the 0 position, and see if it still comes on.

Sounds like the brake light, a lower or the high center mount.

to chime in... but there is a small bulb in the tail light... that one has caught me..

also license plate light....

it is not the obvious ones!

Don't forget to check the back up lights and left rear "fog (tail) light" too.

light out
 

Aamge 55,

If you have not located the bad light yet, consider this:

Check which system the warning lights on either side of the "bulb out" warning light address (I think one is "low washer fluid", do not remember the other) and make sure those systems are working OK. If not ... for example, if your washer fluid is low, it may be because someone replaced a burnt out bulb in your instrument cluster and mistakenly put the "bulb out" bulb in the wrong hole - if so, next time you have the cluster out you will need to switch those two bulbs.

No need asking how I know this can happen.

to add to what others have noted - the bulb out indicator can only the lights that are currently suppose to be on. So - if you start the car (without pushing the brake pedal or turning on the headlights) the lamp shouldn't be lit, period.

If it is - I would guess that KermitF is on to your problem - the MIL is for some other system.

If it is not on - press the brake pedal - does it come on then? If so, you know it is in the brake lights...

Skiier3_9, I agree with you, it should not be on. When I start the car, without it in gear, without turning any lights on, that warning light is on. This warning light should indicate which light is in use that is currently burnt out. So rear brakes, fogs wouldn't have triggered it.

As for KermitF's suggestion, we've had this car since new, so I am 99.9% sure nobody's been inside the instrument cluster to swap bulbs yet. Lee, the license plate lights have caught me too, couple of times at the inspection station. So that's the first place I look now.

Also - to head off another cause: I've heard that changing to lower wattage LED bulbs will cause this, but I don't have any. All the bulbs have been on the car for at least a couple of years, so it's not from a recent change.

I'm going to take a comprehensive look tomorrow. Maybe swap out each bulb one by one to see if I can isolate it. Thanks for all the suggestions so far.

The mystery continues.....

As far as I know ( and that's not much ), it could be a suspect connection between bulb/socket.
May as well check all the sockets when you're pulling bulbs anyway. ;)

If you didn't know, you are supposed to used the european wattage bulbs, not the domestic ones. How's your brakelight switch?

After going through each bulb, finding them all good. The warning light disappeared. Arrrrgh! It was after I checked the left rear set of light clusters it went away. Maybe it's like what Manny said - just a matter of seating it in the socket.

Nevertheless, it's off now. Still annoys me that I haven't found the cause.

Wd40
 

a tiny dab , on the contact points (clean) ,of each bulb [and clean contact
points of each socket]will make this annoying situation less likely in the future.

I have had problems with the contacts in the left rear tail light assembly too. I think it was corrosion, because when I took all the bulbs out and hit the contacts with some very fine grit sandpaper, it went away. Hasn't returned for about five years now.

To ressurect an old thread, I have the bulb lamp warning lot on only when I turn on the lights on my new to me W124 Cab. I had a license plate bulb out, traced it to a bad wire in the hinge of the trunk and thought that would do it.

The license plate lights are now on, and all the other lights seem to work, but I still get the lamp bulb warning when I turn on either running lights or headlights. What am I missing?
Regards,
Jerry

Check to be sure that they are all the proper wattage, it is in your owner's manual and molded into the tail-light bulb holder.

The side-lights in the tail-lights are notorious. It is an outside light system only, not inside lights, and as it comes on without the headlamps or foglamps on I would eliminate them.

Can also be the lamp/warning module itself, open the cover behind the fusebox and it is the longest plug-in module.