I recently bought a 1984 300CD which would only shut off if the blower motor was on. The A/C did not work and the key switch was balky. When the key switch finally froze up, I had to have the switch replaced. The mechanic charged the A/C, and it started to work. The car was always quite slow, shifting quickly to high gear. Soon after getting the repairs done, the A/C suddenly quit, the car would not shut off, the central locking system quit. I bought a repair manual for the 123 chassis, but it was next to worthless. The few photos in it were nothing like my car, which has automatic climate control (III), and I haven't found a way to identify the components of the vacuum control system. Also, there is a light blue plastic (vacuum?) tube bundled with the other tubes coming from the firewall that is not connected to anything. It seems to have a slight vacuum when I put my finger over the end of it. Any help here would be appreciated. My wife is seriously on my case for buying an old M-B.