1991 300d, the right rear side marker bulb often won't work, which causes the dash to get the warning light.

I'd previously scraped the calcium type buildup on the all of the bulb receptacles and put dielectric grease on the bulb, I've changed the bulb out with a new one but it still doesn't work most of the time. Occasionally it will work. Any ideas of anything else I can do? All the rest of them work, it's just that one.

You may want to check the ground on the light that seldom works.

How do I do that?

Remove the bulb holder and look for the brown ground wire. They can form a bad connection overtime. As I recall, I drilled a hole in the metal bulb holder, terminated the wire with a crimp type ring connector and screwed it into the bulb holder.

Good luck!!!

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Don't overlook the bulb failure module either. All external lighting goes through it and it's a common source of frustration as the solder connections inside break.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Seems like if it's the ground wire, none of the bulbs would work on that side.

I believe the bulbs on the rear of the car are grounded separately from those on the front of the car. A simple way to check is to attach a jumper wire to the bulb holder with the other end on a clean ground. Turn on the lights and if the bulb lights when grounded you have found the problem.

Test with a jumper as Bwhitmore suggested. Other lights working do not prove the ground to be clean tight and proper. It only proves the ground sufficient for the lights that are working. When an electrical problem seems peculiar it is usually an inadequate ground connection.

Good luck!!!

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

I had to wiggle all my bulbs to break up some corrosion on the contacts.

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Tulare County, CA

WTB list: (1983 300d)
-Exterior rocker panels below doors
-Gauge Custer plastic window/indicator icons

(1983 300D Turbo)