Why Won’t My Furnace Ignite?

blue furnace flame

No one likes being left out in the cold by their furnace, especially in the dead of winter! If you’re stuck with a gas furnace that keeps clicking but ends up failing to ignite, there are a few troubleshooting steps you can try that won’t cost you a dime and that don’t require the help of a technician. However, some solutions will require a professional for safety’s sake.

There’s a problem with the thermostat.

Typically, your thermostat should be set to AUTO. In this case, you might need to switch it to ON to get the fan going and see if that resolves the issue--just make sure the thermostat is also set to HEAT. If the thermostat displays an error code, it might need to be reset, repaired, or replaced.

The circuit breaker tripped.

Even though gas furnaces burn gas to create heat, most rely on electricity to ignite when they start up. A brief power surge can cause your furnace to trip the breaker of its respective circuit. Check your circuit breaker box to see if the breaker needs to be flipped back into position so that electricity can flow back through your furnace’s circuit.

The gas supply has been shut off.

Your furnace can’t ignite without gas, so check your gas line’s shut-off valve (located outside) to see if it’s open. When performing repairs, a technician will close the valve and might forget to open it, which could be causing your ignition issue. If you’re not sure where the valve is, you can also test your home’s gas supply by seeing if you can ignite your gas stove or another gas-using appliance.

There’s something wrong with the ignition sensor (or thermocouple).

Newer furnaces have an ignition sensor (aka. flame sensor), and older furnaces with a standing pilot light have a thermocouple. These devices are safety features that prevent gas from building up in your furnace.

  • If the ignition sensor detects that the burners haven’t ignited, it shuts off your furnace’s gas supply.
  • Similarly, the thermocouple will shut off the furnace’s gas supply if it can’t detect the pilot light’s heat.

Sometimes the solution is as easy as cleaning the burners or pilot light. However, the repairs get more complex if they involve replacing components or adjusting the composition of the gas-oxygen mixture supplied to your furnace. It’s best to involve a professional technician to get to the root of the issue safely.

For dependable heating repairs and maintenance in Decatur, you can always rely on Jackson Plumbing, Heating & Cooling. Contact us online, or give us a call today: (256) 304-8883.

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