Hi Everyone,

Need help again on my 1994 S350 diesel again. The driver door will not lock or unlock with the remote, but all other three doors and truck lid lock work just fine. The switch that locks/unlocks door on the dash board doesn't work at all.

Since other door locks are working, I assume the pump should be fine. The switch that locks/unlocks door, could be just switch itself. So I leave that one alone for now.

At the beginning, I thought the problem would be either the actuator, or the tube connects to actuator leaks, or no power feeds to actuator. So I bought a new actuator, disconnected power connector and air tube from old actuator, connected them to new one. I was hoping it will solve the problem, but it didn't! When I use the remote to lock/unlock the door, I can see the new actuator is trying to move, but it barely moves, probably expands/retracts about 1/16 inch and that's it. I disconnected the air tube from the actuator, try to lock/unlock the door, I can hear the air hissing. So what could be the problem? I also switched the driver door, driver side rear door air tube on the pump end, rear door always works, so the pump is definitely OK. Am I getting a defect new actuator? The power feeds to the actuator is not up to standard (volts/amps)? Or the tube leaks so there is no enough force to expand/retracts the actuator? Does it have anything to do with the switch I mention above?

Any help is greatly appreciated! I am really out of idea at this moment, what should I try next? But a new tube, connect the actuator to the pump to eliminate the possibility of leak? Anything else?