Passenger Door Lock
 

This is for a 1981. The key will lock and unlock the drivers door, but will not lock or unlock the the passenger door. The passenger door does lock and unlock with the vacuum system. The key is not the original key.

Any suggestions on where to start?

Sounds like they key you have is the valet key. I bet it doesn't unlock the trunk either.

No the key works in the trunk, but I just talked to my daughter who has a new factory key and she has the same problem. The key turns, but does not lock or unlock.

You will need to remove the screw out of the door edge and slide the door lock out in a forward direction. Then look to see what's busted. Since the car is an 81 it has a little safety feature built into the lock to prevent someome else from doing this and getting a key made at a lock shop without you knowing. To slide the lock out of the door, the key must be inserted and turned.

Peter