w124 speaker problem FIXED
 

On my 1993 300ce, the LEFT front speaker intermittently went in and out, and often made popping sounds. I swapped out the fader switch with a known good one - no change. I inspected the euro speaker plugs that attach to the amp in the trunk, and discovered that one of the wires had come free of however it was attached to the male pin that gets inserted into the amp. I spliced in a good euro plug, connected it to the amp, and clear sound emerged from all 4 speakers. Hope this helps someone.

That Euro speaker plug is one of the worst connector designs of all time. Right up there with the USB.

What's wrong with USB? I've had more trouble with HDMI than anything.

I have problems with 110V Plugs, those two blades keep getting bent and are hard to push in to the wall outlet.

Good work finding the loose connection, may problems are connection/good contact related.