Brake lts inop switch gd bulb good harness good What is wrong???
 

I am having a nightmare troubleshoot problem trying to find out why my brake lights suddenly stopped working. I tested the under the dash switch - it appears to work fine ( out = connected, in = disconnected ) and both bulbs in the rear are good, the wiring harness at the lamp box is good - where can the problem be? Also happened at the same time is the left headlight is not working and it's not the bulb - I replaced it and it still won't work. All fuses are intact.

Brake lts inop switch, bulb, harness good What is wrong???
 

I am having a nightmare troubleshoot problem trying to find out why my brake lights suddenly stopped working. I tested the under the dash switch - it appears to work fine ( out = connected, in = disconnected ) and both bulbs in the rear are good, the wiring harness at the lamp box is good - where can the problem be? Also happened at the same time is the left headlight is not working and it's not the bulb - I replaced it and it still won't work. All fuses are intact.

Oh yeah - car is a Merc 300 CD 1980
 

brake lights don't work even though bulb and pedal switch is good

Check for bad grounds.

I would second the ground issue, you will need a tester . Work back to see where power is interupted. They can be a bugger to track down

I third the ground issue. If you don't have a tester, check, and clean as a matter of course, the brown ground-wire connections at the right of the right headlamp assembly, behind the instrment cluster, and to the right of the right rear lamp assembly. Most MBZ are grounded this way.