Keeping an older furnace in operation often means dealing with many outdated parts. Furnace technology continues to advance as furnaces become more efficient, and ignition systems are one area where modern furnaces differ substantially from their older counterparts. Spark ignition systems are one such outdated component, although they're more modern than pilot lights.
While many modern furnaces use hot surface igniters to light their burners, spark igniters work more like the spark plugs in your car. Note that some manufacturers still use direct spark systems, so it's possible to have this style of igniter even on relatively modern furnaces.
How Is Direct Spark Ignition Different From A Pilot Light?
You probably know about pilot lights if you're familiar with older gas appliances (or even some modern appliances, such as water heaters). Pilot light ignition systems keep a small flame burning at all times, providing the initial heat necessary to ignite the burners when your system demands heat. This approach is, for obvious reasons, relatively inefficient.
Direct ignition systems eliminate the pilot light in favor of electric igniters that light the burners directly. Since your furnace won't use any gas while it isn't running, these systems are far more efficient than pilot light igniters. Direct spark systems use high voltage to create a brief spark, which, in turn, ignites the gas supply to the burners.
How Do You Know If You Have An Ignition Problem?
It might seem like diagnosing ignition problems is relatively easy, but condemning your igniter isn't always the right call. Even older furnaces need to run through a series of safety steps before they ignite, so problems detected by one or more safety sensors or switches can stop your furnace from even trying to ignite.
With a direct spark ignition, one way to know that you may have an ignition problem is if you can hear a rapid series of clicks. The audible clicking you can hear as your furnace ignites is the sound of a high-voltage arc created by the spark igniter. If you can hear this sound, your igniter is producing an arc but failing to light the burners.
How Can You Fix A Faulty Spark Ignition Igniter?
If your furnace doesn't ignite, you'll need an HVAC technician to run through the list of possible causes before replacing parts on your igniter. These issues may include exhaust restrictions, problems with the draft inducer, faulty pressure switches, and more. If none of these issues are at fault, the issue may lie with the direct spark igniter.
Since direct spark igniters are fairly straightforward, the problem typically lies with either the igniter probe itself or the high-voltage relay. An HVAC technician can test these parts for proper operation and replace the faulty component, allowing your furnace to get back on its feet again. For more information on furnace repair, contact a company near you.