'98 S70 93K
This is a little complicated, bear with me...

Symptom: The power locks change the position of the door lock post sticking up through the door, but regardless of the its position the door can be opened from the outside. (against better judgment?) I took apart the door and got the latch assembly out and this is what I found after playing around a bit:
http://web.ics.purdue.edu/~tschaap/volvo.html

Some background first: A and C are parts of one piece. Z is the part that connects to the post that sticks up through the door (the picture shows the assembly 90 degrees clockwise of its proper orientation), and B is the piece ultimately moved by either the power door lock mechanism or lock post. Piece A/C is not currently attached to anything at the bottom and it appears that it needs to be.

How do I know which position is locked and unlocked? Good question. By playing around with piece A/C I discovered that when it's in the position marked as 'locked' in the photos one can't release the latch with the lever (normally) attached to the exterior door handle. In the pictures, the only reason piece A/C is in the correct position after I move part B/Z is because I moved it by hand.

The theory: A and B should be connected somehow and I have lost some piece of who-knows-what to make sure that when the post is moved/power locks activated piece A/C moves in concert with B. The problem is I can't find any "missing" piece in my door. Argh.

Anyone have any thoughts about my mystery connector? Maybe someone has an old lock assembly around somewhere and wants to make a few bucks selling me my missing gizmo?