lamp out monitor

[donwo]

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.