My son's 960 Volvo. Vanity mirror on visor came off. Now, door chime won't stop??

you may have a blown fuse

If the door chime won't stop, it may be due to a damaged actuator in the doorway. Try opening and then closing one door at a time to see if you can find the offender. In the door opening you will find a small switch that when pressed, will compress and register that the door is closed. When the door opens, it expands. Something may have damaged one of these or it may be sticky. Try a bit of lube like WD 40 or something with graphite to see if that helps. Loosening the actuator and checking the wiring attached to it may reveal a bad connection and/or chafed wires that may need to be taped up to eliminate unwanted grounding against the door frame.