Why is my furnace not igniting?

When your furnace is completely dead, check for electrical power to the furnace. Check the house circuit breakers to see if the furnace circuit breaker tripped. Reset the breaker if it tripped. If the furnace still isn’t getting power, check the furnace switch that’s typically located on the wall next to your furnace. The furnace switch is often a simple light switch that shuts off power to the furnace. Turn the furnace switch on if you find it turned off.

If the furnace still has now power at all, it may be time to schedule repair service for your furnace.

Furnace will not ignite

If your furnace won’t ignite even though it has electrical power, make sure the thermostat is set properly. Many home owners have overlooked this basic troubleshooting step and wind up having a service technician come into their home and point out the oversight. You need to have the thermostat set to heat mode at a temperature setting that’s high enough to call for heat before the furnace will ignite.

If the thermostat isn’t working properly, you may be able to replace the thermostat yourself. Replacement thermostats typically have detailed installation instructions so you can quickly install a new thermostat and get your furnace going again. If you plan to replace the thermostat yourself, take a digital photo of the wires connected to your original thermostat because you’ll may need that information to hook up the wires to the new thermostat. If you’re not confident that you can replace the thermostat yourself, have a service technician install a new one.

On some furnaces that use electronic ignition systems, the electronic control will signal an error code when the furnace encounters a problem and won’t work properly. The status LED light on the furnace will flash a number of times to signal the error code. Here’s a list of codes that the LED light will signal on common a common Goodman gas furnace:

• Constantly on. No furnace problems. System is operating normally and no errors detected. LED is off. Electronic control board failure or lack of electrical power. Reset the house circuit breaker for the furnace. If power is okay, replace the electronic control board (with electrical power disconnected to the furnace).

• 1 flash. Furnace attempted unsuccessfully to ignite the burner and start the blower too many times. This code will reset after one hour and the furnace will attempt to start again.

• 2 or 3 flashes. Pressure switch failure or induced draft blower failure. The pressure switch monitors airflow through the induced draft blower. Have a service technician diagnose and repair this failure.

• 4 flashes. Tripped high-limit switch. The high-limit switch trips when it detects that air temperature in the furnace is too high. Check the air filter and replace it if it’s dirty because a clogged air filter can cause the high-limit switch to trip. The high-limit switch will reset after the furnace cools down. If the high-limit switch doesn’t reset or it continues to trip even with a new air filter installed, have a service technician examine and repair the furnace.

• 5 flashes. The control senses a burner flame when the gas valve is shut. A leaky gas valve can cause this failure. Have a service technician repair the furnace.

• 6 flashes. Blown flame rollout fuse. Uncontrolled burner flames tripped the fuse. Have the furnace repaired by a service technician.

• Continuous flashes. The electrical power connections to the furnace are reversed. You’ll typically only see this code when the furnace is being installed or you’re replacing a component and reconnecting wires incorrectly. Reconnect wires correctly or have a service technician repair the furnace.

Furnace clicking but not igniting

When you hear clicking but the furnace failed to ignite, common furnace problems such as a failed ignition sensor, bad igniter, closed gas shut off valve on the gas line or a gas supply problem may be reasons that the furnace failed to ignite. Other problems can also prevent your furnace from igniting even though it clicks to start the ignition process.

Check the troubleshooting tips in the owner’s manual for your furnace. If you can’t get your furnace to ignite after following the troubleshooting tips in the manual, you’ll likely need to have a service technician diagnose and repair the furnace.

To prevent furnace ignition problems, schedule annual maintenance checks for your heating system. A technician will check and adjust all furnace components to ensure smooth furnace operation. Having your furnace maintained yearly won’t just help prevent heating problems, the annual maintenance will also help your furnace last longer.