[Richard / E320]

I'm still sorting out some minor problems or issues on my 1987 420SEL... when I turn on the parking lights or headlights, the 'bulb out' dash warning light comes on. I've checked all parking lights, headlights, turn signals, tail lights and brake lights; all seem okay. I did notice that when I turn on the right or left 'parking' light, nothing comes on.

What might be the problem with the warning light coming on when all bulbs are functioning, but the 'parking' feature isn't working?

Thank you,

 

[Prochambers]

Sounds like those parking lamp bulbs need to be examined closer. The bulb out feature is real sensitive.

 

[ElRojo]

Richard--

My guess is the license plate lamps, under the lip of the trunk. Not something many check, and you didn't mention them in your list. Since these only come on w/ headlights and parking lights, it would make sense. The left/right parking lights do the same as the first "right" click of the headlight switch, just on one side or the other. If the side markers (low filament of the turn signals) come on with the first right click, then I would think you'd still have the left/right parking lights.

Interesting that the "bulb out" lamp only lights when you have headlights/parking lights-- I would have thought it would be on constantly with any bulb out. Perhaps it's a fault somewhere else.

Good luck!

Dave

 

[mckellyb]

Mine behaves the same way, the 'bulb out' light comes on only when the bulb which is burned out is getting power. This is helpful in figuring out where to look, actually.

 

[mrelbe]

All bulbs may seem OK but are they matched? The bulb out sensor compares current draw for both sides. If, for instance, one taillight bulb draws more current than the other one, the sensor will light. This could explain why in either the left or right parking position, the bulb sensor does not light because no comparison takes place.
When replacing a bulb, it is always a good idea to replace both left and right with the same wattage from the same manufacturer.

 

[wbain]

You could also try some LED lights. They never burn out. I put them in the taillights on my FORD.

 

[Richard / E320]

Sounds like those parking lamp bulbs need to be examined closer. The bulb out feature is real sensitive.

Well, here's a lesson: never try to figure out what bulb might be bad in broad daylight! Checked everything out three times and all seemed okay, until I took a better look at dusk. Turns out the passenger-side rear marker light was bad; I didn't even see the bulb the way its tucked into the side of the light housing. Replaced bulb... light works, no warning light on dash!

Also, I discovered that the Left or Right Parking Light feature only works with the engine not running. When checking into the 'bulb out' problem, I had the engine running due to having all the lights turned on and didn't want any battery drain. Ignition cannot be in the 'on' position for the left or Right Parking Light feature.

Thanks to all...

 

[Richard / E320]

Richard--

My guess is the license plate lamps, under the lip of the trunk. Not something many check, and you didn't mention them in your list. Since these only come on w/ headlights and parking lights, it would make sense. The left/right parking lights do the same as the first "right" click of the headlight switch, just on one side or the other. If the side markers (low filament of the turn signals) come on with the first right click, then I would think you'd still have the left/right parking lights.

License plate bulbs would be a good guess, as you don't really think about them when standing behind the vehicle looking at the tail lights hollering 'right turn signal', 'left turn signal', 'brakes', etc. Turned out to be the passenger rear side-marker... thanks for the suggestions...

 

[ElRojo]

No problem! Glad you got it figured out!

D

 

[mtbguy]

thanks for the post guys- I just had this exact problem and the only bulbs I didnt check were the license plate illumination bulbs. That was the problem!

 

[Lars Spain]

Eh, I have the same problem, only on mine it comes on first time I turn on the lights OR hit the brakes! Makes it simple enough, theoretically; somewhere in taillights, but everything checked again and again, and still the same problem...
Going to check taillight grounds connections, as they seems to be the common denominator in my case - looks alright, but....

 

[Chadahar]

Lars,
Maybe a loose bulb in the connector. I had the same problem and found that I had a slightly loose bulb in the connector base. Just loose enough to jiggle on a dirt road and the next time in the car the light would come on. Walk around showed noting out of whack, but once one bulb sorta winked and that was the culprit.

 

[cool_dog_higgins]

I had that happen....and discovered my left-side bulb in the taillight around the corner was loose. Took a while to notice that one!

After I installed headlight flashers, though, that light always comes on when I switch on the high-beams! I don't think there's any way I can fix that.....though it's not a big deal.

 

[NKJohn]

Hey all,

I began to read this thread for edification in the event this warning light would ever come on.

It did three days ago. Jinxed.


I made several walk arounds with the headlights on, and all markers and headlight bulbs were burning brightly. Turn signals worked properly too. I began to think that the warning circuit may have a fault, but then I thought " This is a w126 Mercedes - it could never be wrong."

So with my wife standing behind the car, I pressed the brake pedal and voila, the left brake light was out. The two filament bulb functioned fine as a rear marker though.

Lesson - If you've done the walkaround a dozen times and cannot find a burned bulb, it's probably the brake light!

 

[Lars Spain]

Charlie; yep, that could be it, but... with the combination of driving lights and brake lights? I suppose it could be two different problems though, anything could happen to cars this old ) Sometime soon I will go through the lot, replace all lamps, add new grounds connections etc.
Might even be a fuse problem? The fuses on these cars are hopeless; could easily be a bad connection there (oh the times I had something electrical on strike - and tapping a fuse would bring it back to life