ORIGINAL: Veerzigzag
There are lots of postings on this, and when operating the roof you have to be very careful not to strip the gears that work the arms.
Mine ('89 2.7 Lux) had stripped gears when I got it, and I rebuilt it plus sorted out the slipping clutch, so here are some notes:
(Check Clark's Garage procedures
here - as ever they are superb on the subject)
1. Mine opens when the ignition switch is in position 2 (ie "normal - on") and you press the switch down - it stops on microswitches.
2. It closes (rocker switch upwards) when the ignition switch is in position 2 but sometimes the arms don't stop at the roof-closed position but carry on to their retracted position (as if for roof removal).
THAT IS THE DANGEROUS MOVEMENT - IF THEY CARRY ON GOING, THE SLIPPING CLUTCH
SHOULD PREVENT DAMAGE BUT ONLY IF IT ACTUALLY SLIPS
3. If the roof is in place and the ignition switch is in position 1 (accessories) then pressing the switch upwards moves the arms to the roof-locked position.
Many people, me included, back off the tension on the slipping clutch so that it just works the roof, which is in my case a lot less than the factory setting.
The factory setting on the slipping clutch is quite tight, and is OK when the gears are both working in unison. With wear and stretching of the cables, what is likely to happen is that one arm stops first, the motor strips that gear, followed a moment later by the other one.
The motor, clutch and microswitches are under the side carpet in front of the battery on my '89 model.
My suggestion is to make sure that you never allow the arms to retract fully and hit the end stops; you can take the roof out if they are couple of mm short of the stops.
Operation is all very logical in a strictly Teutonic way, if you have a degree in meta-philosphical analysis that is.