Pilot Light & Ignition Repair
When your furnace will not light, the ignition system is usually the cause. From modern hot surface igniters to electronic spark ignition and older standing pilot lights, Harpeth Air diagnoses and repairs all furnace ignition systems quickly and accurately.
Types of Furnace Ignition Systems
Hot surface igniters are the most common ignition method in modern furnaces. These silicon carbide or silicon nitride elements glow red-hot to ignite the gas burners. They are reliable but have a finite lifespan of three to seven years and are the most frequently replaced furnace component. Electronic spark ignition uses a high-voltage spark to ignite the gas, similar to a gas grill igniter. These systems are durable but can fail due to electrode fouling, gap degradation, or control module failure. Standing pilot lights are found in older furnaces and use a continuously burning small flame to ignite the main burners. While simple and reliable, standing pilots waste gas and are no longer used in new furnace designs.
Common Ignition Problems
Igniter failure is straightforward: the igniter cracks, does not glow, and the gas valve never opens. Replacement is a quick repair. Flame sensor issues cause the furnace to light and then shut off within seconds. The flame sensor detects whether the burner has ignited and carbon buildup prevents detection, triggering a safety shutdown. Thermocouple failure in standing pilot systems prevents the gas valve from opening because the thermocouple cannot detect the pilot flame. Gas valve failures prevent gas flow to the burners entirely regardless of ignition system type.
When to Call for Service
If your furnace is not lighting, check the thermostat settings, verify the gas supply, and check the breaker before calling. If a standing pilot is out, you can attempt to relight it following the instructions on the furnace. However, if the pilot will not stay lit, or if you smell gas, do not continue attempts. Call for professional service. For hot surface igniter and electronic ignition systems, the components are not user-serviceable and require professional diagnosis and replacement.
Frequently Asked Questions
Why does my furnace keep shutting off after a few seconds?
The most common cause is a dirty flame sensor. The sensor cannot detect the burner flame through carbon buildup and signals the control board to shut off gas flow as a safety measure. Cleaning or replacing the flame sensor resolves this issue.
How much does igniter replacement cost?
Hot surface igniter replacement typically costs $150 to $300 including parts and labor. This is one of the most common and affordable furnace repairs.
Should I relight my own pilot light?
If your furnace has a standing pilot with clear relighting instructions, you can try. If the pilot will not stay lit after relighting, or if you smell gas, stop and call for professional service. Modern furnaces with electronic ignition should not be serviced by homeowners.
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