lamp out monitor
 

The lamp out indicator on my 1987 300E is acting strange. When I start the car all of the indicators illuminate and go out as intended. When I step on the brake the lamp out indicator comes on and stays on. I have checked all lamps and they are ok. When I turn the ingnition off and re-start the car the lamp out indicator goes out as designed. As soon as I step on the brake it comes on and stays on. I have checked and re-checked lamps and fuses with no success. Any suggestions wil be greatly appreciated.

Thanks in advance.

It may be the bulb holder for one of the brake light bulbs, according to an earlier thread. http://www.peachparts.com/shopforum/tech-help/17637-left-brake-light-either-stays-doesnt-go-92-300e.html?highlight=bulb+out+brake+pedal

The indicator isn't acting weird. It is designed to come on when the circuit with a bad bulb is energized, and not before, and it resets itself after turning off the ignition.

It is telling you something is amiss in the brake light circuit. Check out JCE's tip above. You should at a minimum remove and replace the brake lamp bulbs, to clean the contacts, and don't forget the 2 bulbs in the third light inside the car.

Make sure to use Osram or OEM replacements, as the resistance is different than domestic bulbs. If I understand correctly, this can cause oddity in the lamp out indicator as well as potential cruise control malfunction.

lamp monitor
 

Duhhhhhhhhhh!

Thanks to all for suggestions. In checking to find the problem with the lamp monitor I forgot to check the third brake light inside the car. Changed bulb, problem solved. :o

Glad to hear it worked out. We've all done that. Unfortunately the manual doesn't explain the bulb out system very well (like to feature I mentioned, where it only goes on when the affected circuit is in use). It's pretty cool, really, when you think about it.

Steve