The warning light that alerts you to light bulb failure stays on even though all exterior lights are working. The only light in the whole car that is burnt out is the one at the tip of the pass. side mirror control, could this be the problem?

Check the third brake light. Often it gets overlooked.

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SANDEEEP
89 300SEL
230,000Km

"Check the third brake light. Often it gets overlooked."

Didn't even think about it, I'll check it. Thanks

If it is the third brake light the warning light should only come on when you apply the brakes. The system is only supposed to tell you a light is not working when you try to turn that light on (when you operate the brake). There are small marker lights at each rear corner that should be on whenever you turn the headlights on. It is difficult to see these lights are even on when the sun is out. Check those out too.

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Jason Priest
1999 E430
1995 E420 - retired
1986 420SEL - retired

thanks for all of your ideas. I've checked everything including the possibility of a dim headlight but the light remains on. Could the power mirror light failure cause the warning light to be on?

the mirror will not cause this warning to illuminate. As one of the other post said check the rear side markers. Sometimes bulbs of different manufactures will cause this problem even if the bulbs look ok. By this I mean bulbs of different makes side to side installed the car. the fix is usually to replace all the bulbs with bulbs from the same package.(I'm talking about taillights). Only the exterior lights will turn the bulb warning light on. Clues to help diagnoses; key on, watch for warning light,Press brake pedal- Brake light bulb, parking light only on- parking light bulb, headlights same thing ,you get the picture. Good Luck,Brian

Do what shooter said, make sure all bulbs are the same wattage.
Also, check the license plate lights and the fuse box.

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)