1999 E300 Brake light - PeachParts Mercedes-Benz Forum

dhake2 · #1 11-03-2016, 09:54 PM

The right brake light on my E300 is not working. I have determined the bulb and socket are OK. The problem is that the brake wire in the wiring harness that plugs into the lens assembly is dead. Does anyone have any ideas on the best way to troubleshoot? Thanks for your help in advance.

jay_bob · #2 11-04-2016, 06:03 AM

That wire from the tail light assembly goes directly to the headlight switch module. All exterior lights are fed through the headlight switch for bulb failure supervision and fusing.

First thing I would check is the fuses which can be accessed behind the triangular panel visible when the drivers door is opened. There is a little rectangular spot in the seam between the panel and the dash board, carefully pry up here to remove the panel. In the back side of the cover there should be a card describing what each fuse is for.

Are the remaining lights in the assembly (tail light and turn signal) working properly? If not that would be a ground problem. The ground for the right tail light assembly goes to a bolt in the trunk near the light assembly. By definition all ground wires are solid brown on a MB.

If that isn't the problem then you will have to remove the dash cover to access the light switch for further troubleshooting. If it goes that far we'll have to give you some advice, it involves taking out the entire dashboard from left to right including the steering wheel. I have done this before.

Murkybenz · #3 11-04-2016, 07:16 PM

Check the multi plug connections on your light switch.
My lights would often go off and come instantly back on or switching to main beam would see the dip beam go out and no main beam unless I pulled it back to flash position.
I changed the switch and upon testing operation before refitting panels I had no dip beam ,turns out the smallest of the four multi plugs was not a good fit (loose) in the switch. The two tangs that held it were not really doing a good job of holding it in place.
Fixing this loose plug fixed my problem which I had put up with for over a year.

dhake2 · #4 11-04-2016, 09:52 PM

Thanks for the feedback. I checked the fuses which appear to be good and all other lights are working. Sounds like I need to check the wiring behind the switch. Any tips on this?

jay_bob · #5 11-05-2016, 07:07 AM

Sounds like you are going to be pulling the dash cover.

Best thing to do is search for W210 Evaporator Replacement on YouTube. There are a couple guys from Taiwan that did one that's pretty good. Fortunately you only have to do the first steps for getting the outer dash cover removed to reveal the light switch.

Be sure to disconnect the battery and wait 10 minutes before removing the steering wheel, due to the air bag. Not only for the accidental deployment risk but it also sets a permanent fault in the SRS that you cannot clear without the HHT/SDS/Xentry dealer tools.

If you end up trying to troubleshoot with the dash cover exposed be sure to reconnect everything before hooking up the battery.