I said I would follow up on what I discovered about my pressurization loss that I previously reported. The door seal switch was somehow turned to the Off position while in flight.

We first looked at if it was possible to accidentally hit the switch and dump the seal pressure. We both feel that in no way did this happen. We have hundreds of pressurized hours and it never happened before.

Secondly, I looked at the switch. I first thought that when in the ON position, the lever was pressing on the padded leather. On close examination the lever just Kisses the leather. I can't see any movement of the leather when switch is in the ON position. Next I tested the Switch detent, the Mfg. says it should have about 2.5 oz. and don't say in which direction or if in both directions. With no air on, the detent is probably 2.5 oz. from OFF to ON but in the opposite direction it is probably half that. At first I thought that this was the problem. I had others check new switches and they seem to be the same. I then Pressurized the door seal and checked the release detent. To my surprise the ON to OFF detent when under pressure is quit strong. I would say more than the 2.5 oz. in the rating spec. and it is very spring loaded from the neutral point to both the OFF and ON position. It is so strongly held in the ON position that one would have to be making a concentrated effort to turn it OFF.

Bottom-line; I still don't know how this switch flipped to the OFF position. And replacing it with a new one doesn't seem to answer any question. Back to the mysteries of flight.