Does it go to a modulating motor? Is it a Potentiometer type control?
Where does the disconnected wire come from or go to?
Does that capillary tube go to some strange place to sense a temperature?
It looks like a White Rogers equivalent to a Honeywell T6031 controller to sense temperatures at remote locations. If it is, there are specific methods for troubleshooting them. Turning the dial makes something work, but not in ways you expect.
Need more information.
This post was edited by an admin on January 19, 2014 11:22 PM.