On Aug 5, 11:21*pm, Bennett wrote:
Does tstat control a relay on furnace that is sticking?


Yes, or a short in the wiring. Should only take 2 wires
to do the control. A third wire is typically used to provide
additional functionality, like power so the thermostat can
be lit up, etc.

And what is the history? Did it ever work? Was it working
and then something was changed?

Also the overall settup isn't clear. In these parts we usually
don't have seperate timer and thermostat. We have a
programmable thermostat that combines temp settings for
various periods with a clock.