The on/off switch that we use to de-energize the trim system failed on my airplane.   The airplane came back from a condition inspection and on my next runup I tried to position the trims before takeoff with no result.  The switch had been turned off.   When I turned it on it seized part way and could not be turned on or off.  I tried for 15 minutes before cancelling the trip and finding another switch.   Cost me a golf game, half a day and a switch.

I took the switch apart today, only two pieces inside.  One plastic rocker had slightly deformed.  Put it back together and it worked perfectly.   My guess is the A&P stepped on the switch during entry/exit during runups and the plastic rocker was pushed into the housing jamming the mechanism.   This is a simple SPST rocker switch made by Eaton on my Legacy.

Paul
N357V