Just remove both seats, fully dismantle the mechanisms, clean and grease everything that needs to, and reassemble. Note all positions and reassemble with things in the same place, otherwise the seat controller may complain and you won't get the full range of adjustment.

The motors have built-in reduction gearing *and* a position sensor, so if you get the position sensor out of sync with the position the seats are in, you're in for some grunt work re-syncing it. BTDT.

The mechanisms can seize -- they did on my '93 940. The cable may be damaged as well, which will make it lock up. Just make sure you do detailed drawings when disassembling, esp. as to where all the washers go! If you have a digital camera with decent lens, do take pictures every step of the way.

When I dismantled it, I took the bearings out of the rails (don't loose any balls nor retainers!) and showered the rails in the bathtub. There was a ton of dirt in them. Then dried them in the oven (250F, 4 hours), greased and reassembled everything. Worked fine ever since.

Cheers, Kuba