Addressing the "err message" in the Nikon D80 caused by the failure of the switch contact in the aperture control unit. The general disassembly of the D80 is not covered here. However, once access is gained to the mirror box, remove the entire aperture control unit assembly. With the aperture control unit assembly removed, remove aperture control unit motor from the assembly. Then remove the bottom of the housing for the contact gear. Finally, access broken plastic post that retains contact on the gear and replace the broken post with appropriately sized screw (a very tiny and short screw will be needed).