I took a look at another diagram and it shows the power side of the center vent switchover valve being supplied directly from F10 (this same fuse supplies power to pushbutton controller, aux fan relay and temp controller).
The ground side of the center vent switchover valve goes back through the pushbutton controller to the temp controller.
So, if you jumped power to the center vent switchover valve, it may be as simple as a fuse. According to this diagram, the center vent switchover valve should have power all the time.
Here is a link to the diagram:
http://www.startekinfo.com/StarTek/outside/12253/program/ETM/ACC83-85.pdf