w201 sunroof stopped working

[weird beard]

At least it was in the fully closed position. My sunroof is supposed to drop down and slide back. Motor is making a clicking noise, like broken gears, when I try to open it (switch is not marked, so may be when I try to close it) You can hear the motor do something in both directions, the one clicks like broken gears, the other just sounds like the motor loading up.

Any thoughts on the cause of failure? too dark right now to bother, will check it out in the morning. Some help with common failure points would help.