The sunroof in my 93 945 jammed in a "partial vent" position - the driver side corner would raise all the way up, but the passenger's side corner remained below the roof line as though it was ready to retract into the sunroof "tub".. I could release the spring holding the headliner panel on the driver side, but not on the passenger side.
I pulled the sunroof motor and installed a manual crank, but still couldn't fix the issue.
So - I pulled the headliner, with the loss of one or two trim pieces (Volvo plastic does not age well) like the rearview mirror trim cover.
That gave me access to the sunroof tub assembly. Disconnected the drain tubes at each corner, and removed all the screws except - one at each rear (tailgate) corner and one at the windshield end, in the middle, the gold-colored bracket by the sunroof motor. Then with helping hands, removed those screws & dropped the tub.
Now to see what is broken/jammed in the sunroof drive system, and lubricate everything.
Something tells me that re-aligning the drive cables and motor may be fun ....