PeachParts Mercedes-Benz Forum - View Single Post - Faulty bulb indicator on, but all lights are fine?

G-Benz · #9 04-04-2005, 01:24 PM

All posts are dead on...simply put, there are many possible scenarios that could set off the light.

I had the phantom light come on twice at different times and was able to eventually solve by inspecting the rear taillight housings.

Over time, the metal conductor rails (where the bulb sockets reside) get unseated and achieve partial (or no) ground. This is enough of a resistance difference to tell the bulb indicator that something is amiss (thus the light comes on).

Easiest test is to turn all of the lights on (engine running) remove the inside taillight covers, and inspect the bulbs. If any of them seem dim by comparison, press firmly against the rail near the affected bulb(s). If the light intensity changes when you do this, you have found your problem.

Generally, pressing down firmly on the rail will result in a "click", indicating that the rail is now reseated. Do this across the entire rail, as it may have been unseated in several places.