Why is this light on?
 

I have a 1992 300E. One of the lights on the dash is lit.

It looks like a light bulb with dashes around it. It's located between the ABS light and the Washer Fluid light.

I'm guessing there may be a bulb out somewhere, but wanted to make sure. I don't have the owners manual.

Check all your bulbs, including licence plate, back-up lights, clearance lights, stop-lights, etc.
Try to find an owners manual. They are probably available on e-bay, pretty cheap. ;)

Sounds like your brake pad wear indicator light.

The brake pad indicater is a few lights to the left.

This is an indication that there is something amiss in the lighting department!

It could be something as simple as a blown lamp or somebody could have fitted incorrect wattage lamps. The system is very sensitive so will detect and annuciate as to what a mere mortal may deem to be an insignificant problem.

As advised above a thorough check (best to have an assistant) and hope you find a blown lamp, if not you will need to methodically work around the car examining each lamp for correct wattage.

Have fun!


PS: My most common lamp failures are tail and stops.

The warning will come on when the faulty circuit is activated, so if turning on the parking lights makes the warning to come on. check all the parking lights incl the license and rear side markers. if stepping on the brake pedal makes it come on, then check all of the brake lights, (remember the center stoplight).

Gilly

FYI,
you can get an owner's manual by calling 1-800-FOR MERC.

This reminds me of the story of 2 Newfies ( Inhabitants of Eastern Canada...no relation ).

They buy a used car.
Perform a pre-trip safety check.
Guy in the drivers seat turns on the turn signal & asks his buddy, standing behind the car, " is it working?", to which his friend replies " yes, no, yes, no ". ;)

I checked the lights and the right front turn signal bulb was blown. Thanks for the help.

Make sure you replace with a similar type and wattage bulb. Anything else will give a false reading and the light will remain lit...