One of the most frustrating malfunctions of a gas furnace is for it to produce no flame at all. This is bad because no flame means no heating at all. You will need to fix the problem as soon as possible, especially if you are in the middle of the cold season. Below are some of the potential issues that can prevent your furnace burners from coming on.
Wrong Thermostat Setting
Your furnace will only light up if it has been instructed to do so, and you can do this by setting the thermostat to heat. Also, the room temperature must be lower than the thermostat temperature setting for the burners to light up. Therefore, check the temperature setting on the thermostat and confirm that the thermostat is set to heat as part of the diagnostic process.
Thermostat Malfunction
If the thermostat is correctly set but the burners are still off, then it might be that the thermostat has malfunctioned. Maybe the thermostat wires are disconnected and the signals are not getting to the furnace. It might also be an internal problem with the thermostat's circuitry, which you should see on the thermostat as an error code.
No Gas
The furnace burners burn fuel to produce heat, and they won't light up if the furnace is not receiving gas. Maybe there is a supply problem to your house, in which case all gas appliances in your house will be affected. Call your utility company to notify them of the problem if that is the case. If other gas appliances are operating as usual, then the problem is with your furnace. This might happen, for example, if the gas valve that controls fuel supply to the furnace is not properly adjusted.
Pilot Light Malfunction
If you have an older furnace that uses a pilot light, then a malfunction or clogging of the pilot light can also prevent the burners from lighting up. The pilot light provides the heat that ignites the fuel in the burners. Maybe the thermocouple, which heats up to ignite the fuel, is not properly adjusted or is broken and needs to be replaced.
Electric Ignition Problems
Newer furnaces use electronic or electric ignition systems instead of pilot lights. An electric ignition system uses electricity to produce an electrical spark that ignites the burners as needed. This means the burners won't light up without electricity (for example, if the breaker has tripped or if there is a blackout in the house). An electrical malfunction of the ignition system can also trigger the same problems.
The above issues should help you diagnose the possible cause of your furnace problems. Contact a heating service if you don't get a diagnosis or if you get a diagnosis and you need a professional solution.
