1979 AUDI 5000 brake lights not coming on

Heiko, Great to see a Type 43 posting! I had similar problems with my 1980 5k - check the two brake switches on the master cylinder and the sockets that plug into the switches - IIRC there's a test in the Bentley Manual to check for correct operation. As the wires to the lights are not on the trunk, hinge wiring will not be a problem, but you should also make sure that the socket assemblies (that plug into the back of the lights, with the reverse, brake, park and turn bulbs mounted in them) - are free from corrosion. You should also check that they are properly grounded - I had to install a separate ground wires (left and right) between the ground portion of the punched metal circuit and the body of the car - using the bolts that hold the lens assembly on. The plug that plugs into the socket can also be the source of poor connections from corrosion, etc. Cheers! Steve Sears