I recently noticed that the third brake like in my E300D was not working, and also did not work with a new bulb. I checked if there was power to the connections where they clip to the car underneath the light assembly and there was not. Unfortunately, that was the extent of my skill at electrical diagnosis. It is far beyond my skill to troubleshoot problems like this and track down the cause, but I have often had good luck with checking things that have failed on other peoples cars. Does anyone have any suggestions?

confirm you have other brake lights.My car won't have any if 3 rd is out.Unhook battery for one minute the lighting computer will reset.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

83W126, I guess you realize that MB brake lights only illuminate with the key in the ignition at Position 2, or with the engine running. With some other manufacturers the brake lights may illuminate without the key in the ignition.

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Fred Hoelzle

Yes, the other brake lights work, and no power to the third brake light with the car running. Does anyone else have any suggestions? I am hoping to avoid having to make the decision whether replacing the car over such a seemingly simple problem or just driving without it even though it makes me uncomfortable is a better choice.

I think I checked the wire too. Mine would not work so I bought after market brake light.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

I have a '98 e300 and my third brake light failed twice. The problem both times was burnt contacts (metal strips) on the bottom of the unit. The first time, I just cleaned the bad contact and added a little solder. It worked for three years. The second time, I bought a new light at a Mercedes dealer for $55.00 as I felt it would not take additional solder. I thought it was a good price and then discovered that Peach Parts was selling the same unit for $35.00.

This is a Benz World thread that I found helpful:

Third Brake Light Repair '97 - Mercedes-Benz Forum

It is for a '97 light, but it is the same as on a '98.

This is the link for the PeacPart brake light.

1998 Mercedes-Benz E300 Turbodiesel Sedan - Lights and Lenses - Page 7

Thanks for the suggestion on the brake light, I actually got one at the dealer and put it in, but it still doesn't work. Part of why I hate problems like this, something similar happened on the Alfa Milano I used to drive where it kept blowing the brake light fuse, and I had no idea what to do after checking a few obvious problems, but eventually someone said "there is a crimped on part of the ciggarette lighter in the dash that has probably come loose and shorts out the wires when you go over a bump, check that and it should fix your problem". Sure enough I checked and it took me about 5 minutes to fix it, but even if someone had offered me a million dollers to find the problem I am sure I never would have found it. I dont even know how people learn to do stuff like that. I may end up just trying to sell this car once I finish fixing the old subaru I have, because I really don't want to drive a car with missing brake lights.