dash warning light

Help....the warning light on the dash indicating a light is out ,,,comes on constantly and cannot find a light out on the 1991 420 sel,,if i leave the key turned to the on position for a short time b- 4 starting up it will not light up until i turn off engine ..small but mind shaking,,,thanks jack

[G-Benz]

Bulbs can be operational and still trigger the "bulb-out" indicator...a bulb that is dark gray will signal impending failure...but still illuminate.

You can probably rule out a number of bulbs through common sense. If if comes on without the headlight switch being activated, you can rule out those bulbs (including the license plate light). Comes on when braking? Check brake light bulbs (including the third brake light).

Comes on when first starting, but goes off when switching on headlights? You have a grounding problem on one of the taillight housings. In that case, you must open the housing and jiggle each of the bulbs to see which one does not have proper contact. When you find it, the "bulb indicator in the dash should go off. Then get some needle-nosed pliers and adjust the socket so that the bulb can seat more firmly.

Also, remember to replace bad bulbs with the correct wattage (usually 10W for the bitty bulbs and 22W for the rest). Use Sylvania, Philips, or OSRAM bulbs with the nickel-plated housings, not the gold-anodized domestic jobbies...they will set off false ohm readings and light up your dash indicator for no reason!

[sunil190e-1.8]

do check your rear licence plate bulbs-these re often overlooked.

also if bulbs of the wrong wattage are fitted,they will cause the warning light to come .

hope this helps

[bd37703]

I just got the dash warning light as well ..... the bulb that needed replacement was the brake light bulb in the middle of the rear windshield .... good luck!