I have a 1998 Audi A6 Quattro wagon. My backseat seat belt on the driver's side is locked up and can't be used. The housing for the seat belt is inside the back cushion. How do you access it to unlock it?

 

I don't know, but seat belts are one of those life time warranty items. Dealer should take care of it for you.

 

The lower rear seat is held by two screws near the floor. Look in the owners manual, which should be kept in the glove compartment. The battery is under the rear seat. The seatbelt may have got misplaced when the battery was replaced.