Brake switch activates brake lights--cruise is on the same circuit, at least on some MB models--the MB CC unit is sensitive so that if a brake light is out more amperage goes to the cruise circuit than usual, possibly causing damage and then messing other things up.

__________________
________________________
2002 Mercedes-Benz E320 4Matic
1995 Mercedes-Benz E320 Wagon
2005 Land Rover LR3 V8 SE
1999 Audi A8 4.2L quattro