Center air vents stopped blowing air?

Being it's a 1992 it will have vacuum-controlled doors in the HVAC. As such there are two items that can fail, a control solenoid or the vacuum motor that moves the doors. The problem is that pretty much none of the parts are available outside either an older dealer or a specialty Jaguar shop. You will also want the factory service information, which unfortunately they didn't release to places other than the dealerships.