Most gas furnaces are outfitted with an electronic igniter that lights the gas. In the furnace models that use this igniter, there's no pilot light to light. If you're familiar with the older pilot light system, you may recall being able to light it yourself if it went out. If the igniter on your furnace fails, you'll typically need to turn to an HVAC technician for replacement. Luckily, you can reset it on your own to see if that will clear the error before you invest in a service call. Here are some tips to help you locate and reset the igniter yourself.
Finding the Igniter
Turn off the circuit breaker that feeds the power to your furnace. You should find the breaker in your home's main electrical panel. Most panels are clearly labeled, making it easy to identify the one that controls the furnace. If your home's furnace isn't marked on the circuit breaker, you'll have to shut off the main breaker that controls your home's primary electrical feed. This will disable your lights and all of your electricity, so you'll need a flashlight to see where you're working.
Pull the cover panel off the burner compartment on the front of the furnace. Look for the valve that controls the gas feed. The burner and valve may be located at either the top or bottom of the compartment, depending on the style of your furnace.
Look for the small pilot tube connected to the control valve. Then, follow that tube until it terminates at the burner. The gas line that attaches to the burner assembly is the one that holds the spark igniter and the pilot tube. You'll know the spark igniter on sight – it is an inch-long probe connected to a ceramic tube. There's an electrical wire connected to the opposite end of the ceramic tube. There may even be a flame sensor connected to one end of the igniter.
Some furnace models have a hot-surface igniter. You'll know if your furnace has one if you see a flat piece of metal instead of a round probe. In that case, the metal will be connected to a square ceramic block that has two wires attached to the opposite side. Hot-surface igniters have no flame sensor in the line.
Resetting the Igniter
Once you have found the igniter, it's time to reset it. Locate the switch on the side of the igniter and flip it to the "OFF" position. Leave the igniter off for several minutes to allow the system to clear. In some systems, there may be a red button beside the igniter that you'll have to push and hold. If there's a red button instead of a switch, push and release the button instead.
Put the burner door back in place, making sure that it's secured. Most furnaces have a safety switch that prevents the furnace from starting until the burner door is locked in place. Once the burner door is secure, restore the power at the breaker panel.
Once you have restored power to the furnace, test the igniter. Set your thermostat to engage the furnace. Make sure that heat comes out when the system engages. If the furnace turns on but no heat comes out, turn the furnace off completely and call an HVAC technician to replace the igniter.
Your home furnace can be an intimidating, complex unit, but when you understand the components inside the case, it's easier to navigate. With the information here, you can not only find but also reset the igniter. This may save you the cost of an emergency call, especially if the system malfunctions when the temperatures drop.