I've been thinking about how to rig the "door unlatched" light on mine as well, so the posts on this subject got me to thinking.  At first I was trying to rig a switch on the fuselage since any switch in the door would be disconnected when the door is fully opened (the 3-contact interface goes open when you raise the door).  But on the fuselage there is no room to put a switch where you really need it as the tip of the lock pawl comes up against the door frame in the latched position - no room.  I was just thinking that I could rig up 2 switches, one that says the pawl is out far enough and the other that says it is up.  They would be wired in series in such a way that the only way for the light to go out would be for the pawl to be out AND up.  Kind of complicated.

The simple way might be to do as suggested and use the third door contact to complete the circuit.  The light would go out if the door was EITHER latched or fully open.  Fully open is obvious so all you really are worried about is that the door is physically closed but the latch isn't fully latched.  A simple switch inside the door would do that.  This might be the most acceptable compromise.

A third way would be to have the switch inside the door but make it so that you have to have continuity to make the light go out, probably with an inverting relay.  In that case the light would be on with the door in any position and it would only go out if it was fully latched.

Gary Casey