Chris,
The digital clock in our '85 was giving trouble with changing the hours.  Then the "button" got stuck and the hours kept turning over.  The clock was easy enough to remove from the instrument cluster.  Once the clock was out I could see the button you push from the front is just a piece of plastic that pushes a button on the clock.  The piece of plastic had gone in too far and was stuck behind the hole it moves in.  By putting the plastic piece back in its hole the unit was returned to working order.
Good luck.
George
'85 westfalia