Furnace shows E9 and locks out; may occur after repeated failed ignition or flame loss events.

Safety: Turn off power and gas before cleaning or removing burner components.

Steps:

• Reset the furnace by turning power off for 30 seconds and back on. Observe the ignition sequence.
• Clean the flame sensor as described in the E4 entry.
• Inspect the hot surface ignitor for cracks or white spots; if damaged, replace with the correct Westinghouse-rated ignitor.
• Vacuum burner inlets and crossover ports with a soft brush to remove dust and rust.
• If flames light but drop out when the blower starts, a professional should check gas pressure and combustion air.

Note: Do not repeatedly reset a furnace that continues to lock out; have a technician evaluate the gas train and combustion.