I have a 1989 MB 560SEL with the factory Becker Stereo system. The sound on the entire left side would sometimes disappear and come back on unpredictably. Would you tell me what is the problem? How and where would I start looking for and fix the problem?

STL

Could be as simple as the connection at the fader switch. The system has two seperate amps. behind the rear seat & a preamp on the radio. Any of these can cause one channel to quit. Possibly the rear amps can be swapped (they are the same) to see if the problem follows the one that quits.