BMW Repair: BRAKE LIGHTS, brake light switch, bmw forums

Question
83 733i  
NO BRAKE LIGHTS
BULBS GOOD
FUSE GOOD

Answer
look at the brake petal and follow it up into the dash where there is a switch. Disconnect the switch and touch the two wires together (ignition on) and the lights should come on if the problem is in the switch.  If they don't come on, then suspect a bad ground or disconected wire.  My guess is that it is the brake light switch.

more info:
http://www.roadfly.org/bmw/forums/
-cheers