Brake bulb failure
 

One of my brake lights on my 89 560sl is not working. Changed the bulb,checked the wire harness for a splice but i can seem to find anything wrong. BTW all the other bulbs including the other brake bulb on that side are working properly...Any thoughts? Thx

Cruise Control
 

On W123's the Cruse Control picks up it's ground thru the Brake Lights......at least 1 of the Brake Light filaments must be intact to enable the Cruse Control....power to the Brake Lights causes the Cruise to drop out (electrically canceling the ground)......

I don't have any schematics for your car, but knowing the Germans, if it is working soundly, incorporate it in the next design......so you might look at this section of the proper schematic.......

at least that is my understanding of how it works.....on a W123....

SB

Cruise control still works

Run a Jumper wire from one side to the other.. #16 wire.. should fix it..

actually, the cruise control was not working. I replaced the fuse and now the brake lights are fine. However, the alarm and key/light buzzer are now not working. I believe I have replaced all the correct fuses (even the two under the hood by the passenger side, allthough I only had one red left) is there something else I should check ? Thanks again.