Identify a common reason for furnace ignition failure and a simple diagnostic check.

Identify a common reason for furnace ignition failure and a simple diagnostic check.

• A. Faulty or dirty ignition/igniter; check for proper flame signal or spark, and verify gas valve operation and wiring continuity.
• B. Worn blower belt causing poor airflow.
• C. Faulty thermostat sensor causing no heating call.
• D. Clogged condensate drain causing safety shutoff.

Answer: (A)

Ignition problems in furnaces almost always trace to the ignition path—the igniter itself or the flame-sensing circuit. If the igniter is dirty, cracked, or worn, it may not heat to the temperature needed to ignite the gas. If the flame sensor doesn’t sense a flame, the control will shut the gas valve off as a safety measure, preventing ignition from continuing. A simple diagnostic is to verify the ignition signal directly: check that the igniter delivers a spark or glows when the heat call is made, and confirm there is a proper flame signal from the flame sensor. At the same time, ensure the gas valve opens when the ignition signal is present and that the wiring to both the igniter and the gas valve is continuous and secure. If the igniter appears physically damaged, is dirty, or the flame signal is absent despite a good gas supply, addressing the igniter or flame sensor is usually the fix.

Ignition problems in furnaces almost always trace to the ignition path—the igniter itself or the flame-sensing circuit. If the igniter is dirty, cracked, or worn, it may not heat to the temperature needed to ignite the gas. If the flame sensor doesn’t sense a flame, the control will shut the gas valve off as a safety measure, preventing ignition from continuing.

A simple diagnostic is to verify the ignition signal directly: check that the igniter delivers a spark or glows when the heat call is made, and confirm there is a proper flame signal from the flame sensor. At the same time, ensure the gas valve opens when the ignition signal is present and that the wiring to both the igniter and the gas valve is continuous and secure. If the igniter appears physically damaged, is dirty, or the flame signal is absent despite a good gas supply, addressing the igniter or flame sensor is usually the fix.