Awl --
A perhaps inneresting electrical teaser:
I've got a chronothermIII thermostat on a gas furnace.
I found the two wires for the furnace (as opposed to the two wires for the A/C), and observed that the III actually energizes these two wires with 24 V -- iow, there does not seem to be an external or furnace-supplied 24 V for the heating circuit. ie, the III is not simply acting like a mercury switch, it is actually supplying 24 V power to the furnace controller.
Ergo, if I disonnect these two wires, and jump them, nothing should happen, and indeed nothing does. In an old mercury-type stat, jumping the wires
*would* kick in the furnace.
OK....
BUT,
If the wires are disconnected from the III, and I energize them with a separate 24 V, the furnace does not go on either!!
The furnace will only go on if the two wires are receiving the 24 V from the III.
Could the two wires for the A/C somehow be mixed up in this? Those wires DO have an external 24 V transformer, which the III "knows" about, as it will register a " -AC " on the lcd if those two are disconnected..
But still, with the furnace wires isolated (off the III), either jumping them OR providing them with 24 V should kick in the furnace, right? But no go.
Iny idears?