Clicking window motor
 

Car is a 92 400E. Front passenger window does not move at all. I can hear a clicking noise at the window when operating the switch. There's no sign of any stress, like a jammed regulator or something - just a slight clicking noise - like the motor is trying to kick in but it can't quite pull it off. It seems to me the console switch must be fine, or it wouldn't be able to generate a click at the window. And there's no sign that I can see that the regulator is not working.

So what my next step? - short of just buying a new motor and trying it out.

Remove the door panel first to find out is your motor or window reg cause problem before you buying any new parts.

When I bought it my 300CD would raise the passenger window 1/2way before it would stop then I'd hear a click-click-click-click-click. Turned out to be broken teeth on the window regulator arm.

You'll need to pull the regulator/motor to be able to see where the problem lies.

The panel is off. It does not sound like regulator tooth slipping - not that mechanical, or loud. It's just a click - like an electrical switch or relay trying to click over but not quite able to. And the click is coming from the door, not the console. I feel certain that a new motor would solve the problem - just wondering if there's a cheaper way. I bought a voltmeter today - now I've just got to figure out how to use it.

Sounds Like Regulator Problem
 

I had the same problem with my '92 300e and it turned out the be the regulator. It's pretty common for the teeth to wear off after ten years.