There is a switch that turns on the brake indicator light when the emergency brake is on. It is a 1975 450SL. Does anyone know where the switch is located and how to get at it?

 

More than likely the switch is just above the pedal arm (if you have a foot brake) just like current model rear brake lights work. The switch will be bolted to the frame. Good luck

 

Today - actually, I was removing the vacuum brake drum (lying 180degree of normal, with my foot up in the air) in the cockpit. I was curious about the park brakes as well, and found out it's a little switch at the end of the "hand brake" pedal that do the switching. It's a one wire only (the other one go trough the chassis). Its looks like very easy to replace (but you must be an acrobat - like me!)