For a long time, many furnaces relied on a standing pilot light to work. The standing pilot is a small gas flame that remains ignited throughout. You’ll know you have one if you can see a small green bulb in front of a small flame on your furnace.
Unfortunately, standing pilot lights are unreliable. They are also very wasteful. Constantly burning gas, even if it’s just a tiny light, can lead to a sizeable bill at the end of the year.
For the above reasons, homeowners slowly began to replace standing pilot lights with electronic ignition systems. Electronic ignition systems are not just more efficient but also easier to maintain. They are also less of a safety risk.
There are two main categories of electronic ignition systems – hot surface ignition systems and intermittent pilot systems. Hot surface ignition systems use electricity.
When the heating system becomes warm enough, the gas flows into the burner, and the ignitor lights up. Meanwhile, intermittent systems use an electric spark that automatically turns ON the pilot light to detect gas supply.
However, electronic ignition systems, too, aren’t without fault. Although way superior to traditional standing pilot lights, the ignition system can fail, cutting gas supply to the burner, and rendering the furnace unable to light.
So, what can cause the electronic ignition furnace to fail, and what can you do about it?
Signs You Have a Furnace Ignitor Problem
A furnace that refuses to ignite could be a result of many reasons. However, a few specific indicators may point to a faulty ignitor.
A faulty ignitor won’t produce the spark necessary to light the burner to heat the air headed for your home. Without it, the heater will blow cold air (at room temperature). However, you need to rule out a few things to narrow down the issue to a faulty ignitor.
First, check the thermostat to ensure that it’s set to “heat.” Secondly, double-check the thermostat to ensure that the temperature is high enough to signal the furnace to blow hot air. After ruling out thermostat issues, the next likely issue is a faulty thermostat.
Furnace Won’t Turn On Automatically
Something else you need to observe is whether the furnace comes ON automatically when the temperature drops below the thermostat settings. If the heater remains OFF no matter how cold it gets, you likely have a furnace ignitor problem.
Perform the two thermostat checks above as you narrow down on the potential issue. Additionally, check the breaker box to make sure the furnace switch hasn’t tripped. If the breaker is ON, you either have an ignitor problem or a more complex electrical issue.
Furnace Stops Blowing Suddenly
The standard furnace has built-in fail-safe mechanisms to keep you and the home safe in case of an issue. For this reason, the furnace suddenly going off in the middle of a heating process is usually one of the surest indicators of a significant issue. Many times, it’s the ignitor.
However, you need to rule out a few factors first. For instance, check whether the filters are in good working condition to rule out filter issues. Additionally, check for debris. A dirty furnace can also go off suddenly. If the filters are good and there’s no dirt buildup, the next likely culprit is the ignitor.
Furnace Starts Stops, then Starts Again
The electrical ignitor needs to hold a charge long enough to heat the furnace air. However, an old, worn-out ignitor may not hold enough charge to heat the furnace air.
It starts and stops then starts again because most furnaces have a safety mechanism that delays the system for 60 seconds between restarts.
Keep in mind that an ignitor that goes on-off repeatedly is terrible for your furnace. Therefore, you need to address the issue right away.
Furnace Clicks On But Does not Fire Up
Finally, you can also listen out for the “click” sound to verify that you have a broken ignitor or ignitor-related issue. The “clicking” sound from the furnace right before the air starts blowing is usually the ignitor generating a spark that ignites the gas connected to your furnace.
This, however, only applies to intermittent pilot systems. Hot surface pilot systems don’t produce a spark.
If you hear the spark, but hot air doesn’t blow out immediately after, you could have a malfunctioned electric ignitor.
Common Ignitor Problems and Solutions
Now that you know how to look out for electrical furnace ignitor issues let’s discuss the two most common problems and solutions.
1. Damaged or Dead Furnace Ignitor
The furnace ignitor can become damaged due to wear and tear. Indeed, typically, you’ll replace the ignitor twice or thrice before replacing the furnace.
Electric ignitors can also become damaged due to power surges. This is especially true for hot surface ignition systems. If the area is prone to power surges, it can cause the ignitor filaments to burn, totally damaging the unit.
The worst part is that confirming that the furnace ignitor is dead or damaged is a challenging task that requires some electrical know-how.
If you wish, you can avoid the lengthy process by purchasing a replacement ignitor at about $15. Otherwise, you need an electrical multimeter to troubleshoot the bad ignitor. Proceed as follows;
- Turn off the furnace at the electrical switch. The switch looks like a standards light switch.
- Remove the top panel to locate the ignitor. It’s a small decide connected between the electrical wires and the furnace near the gas input. A typical electrical ignitor has a white ceramic base with a black “stick” extending into the furnace port.
- Remove the screws attaching it to the furnace, pull out the igniter, and unplug it from the wiring harness.
- Inspect the igniter for cracks. If it has any, it’s almost certainly damaged, no matter how small the cracks. However, if you don’t see any cracks, move to the next step.
- Check to see if it’s getting power. You’ll know that an electrical furnace ignitor gets power if the inducer motor starts when you turn on the power switch.
- Check it with the meter. Place the meter leads into the plug inside the furnace, one in each hole, taking caution not to push the leads too deep into the plug. Then check your meter readings. If it reads +/-120V, it means that the meter was getting power but not responding. Therefore, it’s bad.
- Check resistance reading to verify your findings. Turn the meter to the ohms setting (resistance is measured in ohms). With the ignitor still disconnected from the furnace wiring, take the reading. Any reading from 40 to around 200 ohms is good and indicates you have a good ignitor. However, readings below 40 ohms mean you have a dead or very weak ignitor. Readings beyond 200 ohms are also bad as they often indicate an ignitor that’s wearing out.
Solution: Your next course of action will depend on your findings. If you find that the ignitor is still in good condition, then you’ve just confirmed that you have a different problem, perhaps not even related to the furnace. However, if you confirm that the ignitor is damaged, you need to replace it.
We strongly advise against DIY electric igniter replacement. For one, you may bring in the wrong replacement ignitor. Secondly, you may install it wrongly. Both of these expose you and your family to grave danger. You may also damage the furnace.
The average replacement cost is $75, including a $60 labor charge. However, depending on location and other factors, such as timing, you may pay up to $200.
2. The Ignitor is Off
Yes, the electric ignitor can be ON or OFF. If it’s ON, it will usually work. However, when it’s off, it cannot ignite the furnace. A typical instance when the ignitor may switch from an ON to OFF is when temperatures rise above pre-defined temperatures inside the gas chamber.
Gas furnaces come with several limit switches designed to ensure the safety of the equipment and the user(s). one of these is the rollout limit switch. The rollout limit switch primarily cuts gas supply and shuts off the heater if overheating is detected or if flames rollout of pre-defined zones within the heat exchange.
The first thing the rollout does to shut off the furnace in case of overheating or flame rollout is to turn the ignitor OFF. Unfortunately, clogged filters can also cause the limit switch to turn off the ignitor prematurely.
Solution: You don’t need to replace an ignitor that’s flipped to an OFF position. Instead, you’re required to reset it.
To rest the ignitor on your furnace, begin by shutting off the power supply to the heater. Do this at the switch to eliminate the risk of electric shocks when handling the unit. With that done, remove the burner door to reveal the ignitor.
First, check whether it’s ON or OFF. If it’s ON, then you have a different problem. Perhaps the ignitor is dead, or maybe it’s not an ignitor issue in the first place. However, if it’s “OFF,” you can switch it ON and turn back the power source.
However, it’s important to mention that sometimes the ignitor may merely be “blocked” internally. Resetting can help “unshackle” the internal components. So, if you check the unit and find that it’s ON, you may want to switch it OFF and back ON to see if anything changes. Leave it OFF for about five minutes. Then, switch it back ON, turn on the power, and restart the furnace to see if it works. If it doesn’t, consider it damaged or dead and find a replacement.
That’s it. Now you know how electric ignition systems work, how to diagnose a malfunctioned ignitor, and even what to do if your ignitor is damaged or dead.