I have a 2010 ML350 Bluetec. Recently the dash displayed messages regarding rear brake lights, and I dove in.

I thought I would seize the opportunity to go LED for the rear brake lamps. This worked in 75% of the locations. For the passenger side rear main brake light, an LED bulb will not work. A conventional bulb in that spot works. I tested the LED bulbs that I tried in other locations, and they worked.

This is confusing. I am aware of the repair kit with the extra grounding wire, and I can certainly install that if needed. I just expected that if a conventional bulb worked in that socket, then an LED lamp should as well.

Does anyone have a good explanation for why a known good LED brake lamp won't work when a filament bulb does?

Thanks!
Tom

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2016 E350 4matic wagon
2010 ML350 Bluetec
1995 E300D Gone, but not forgotten.