How Do You Repair a Gas Furnace That Won't Start?

repair-gas-furnace-won-t-start Credit: Dwight Sipler/CC-BY 2.0

A gas furnace that does not start sometimes requires relighting the pilot light. After waiting a few minutes for fumes to clear the area, the owner can turn the dial to pilot, press the red button, and light the pilot. Holding the button down for 30 seconds warms the thermocouple.

Gas furnaces often require simple steps to start. If the thermostat is set at temperature cooler than that in the home, the furnace does not start. Setting the temperature higher starts it heating.

The air handler requires electricity to operate. A circuit breaker that is off prevents if from starting. As a result, once the temperature inside the furnace reaches a set temperature it automatically extinguishes the burner. Owners should check the electrical panel to ensure all breakers are in the on position.

In some instances, the furnace does not start due to a lack of fuel. With propane furnaces, it is necessary to check the tank for fuel. If the burner on a gas stove or water heater is working, fuel is available to the furnace. Installers add a valve in the gas line that supplies the furnace. It should be parallel with the pipe to ensure gas flow. Once gas is available again, owners should light the standing pilot.