Gas furnaces often perform more functions than it may appear. For example, your furnace may have an integrated furnace control that regulates the amount of gas that goes into the furnace. Other furnaces also have direct spark ignitions, which means there is no need for a standing pilot light. You can reset the furnace if it is having problems running properly.
Flip the switch on the thermostat to the "Off" position.
Flip the switch in the breaker box that provides power to the furnace to "Off."
Remove the panel on the furnace by lifting up on it and pulling out.
Move the gas control valve to "Off."
Wait about five minutes. The gas needs to clear out of the system. Smell for gas after five minutes before continuing.
Move the gas control valve back to the "On" position.
Slide the furnace door downward back into place.
Slide the breaker box switch back to the "On" position.
Turn the thermostat back on.