Rick, sounds a a bit like a bad fader but, when you disconnected the fader you said only the passenger dash speaker quit. Does that mean you had still had sound on another speaker in the system with the fader pulled???
If you had your meter set to Amps when you measured the door speaker wires, it is likely you would blow a fuse. (Use 3v AC setting and check for voltage.). But it also indicates you have a connection back to the amp. Was it the amp fuse that blew?
Trace the signal (3v AC meter will work OK). Play some music, preferably a tape with even volume. Set fader to middle. There are many configurations in MB models and I do not have a wiring diagram for yours so this is just a guess. Console mounted fader on all my cars are the same though. Here is how you can test fader signals:
- Most have Left and Right coming out of the radio head unit (or out of a trunk mounted tuner) into the fader (measure input pins S1 and S2 on fader)
- The S2 (left) input splits into E2 (frt/Left) and A2 (rear/left) (measure at those pins) You can check fader by watching voltage as you move fader knob. Voltage will be erratic due to music but you should note a relative change.
- The S1 (right) input splits into E1 (frt/Right) and A1 (rear/Right) (measure at those pins)
- If all is OK at fader, note the wire colors at E2, A2, E1,A1, and measure signals at Amplifier input.
If all that checks out, trace the amp output signals (they naturally will be a high voltage with the same music and fader setting). Usually the front dash and front door speakers run off the same amplifier output, so having a right dash speaker work but not the right front door work is a clue. If yours is wired that way, you need to trace the wires carefully and check for bad filter components in the front (caps or coils) in the front speakers.
Also note that some of these cars have a trunk mounted tuner/preamp and smaller two channel amps mounted behind the seats. That changes the test procedure a bit.
Scott D