We manually wind the valves for a certain chk we do and as soon as you disconnect the canon plug for these valves you loose your indication and it goes blank. If you lock a valve in a certain position for an MEL you have to disconnect the plug because you can not wind it with the plug on. With the plug on it will always run to the position that the pax temp master selector knob is set to in the cockpit, through the zone temp controller. The valves are under control of the zone temp controller it feeds the position signal from the valve back to the ztc then to eicas. Its not a rvdt it is a potentiometer. The MEL will tell you to wind the manual drive with an allen key so many turns. 30% open is 3/4 of a turn from the closed position. Hope this helps.