How To Turn On Furnace Without Thermostat. You can do this by going to your breaker box and flipping off the respective switches. It's a very simple millivolt setup.
Leave the power to the furnace on. If the furnace has an aux switch inside of the furnace that forces the fan to run, the wiring is simple. This is a common way of resetting to restart the furnace.
To reset this circuit breaker, first turn the thermostat to the lowest setting to prevent the furnace from starting up at the instant you reset the breaker.
This will allow either switch to turn the fan on. Set the thermostat to a high temperature setting, and observe the furnaces's behavior. Set the thermostat to heat and the fan to auto. It's controlled by an analog dial based humidistat at the.