Furnace intermittently shuts down; status LED shows 9 flashes repeating; may be accompanied by blower running unexpectedly.

Safety: Electrical work should comply with local codes. If you are not comfortable working with 120 VAC wiring, contact an electrician or HVAC technician.

Steps to check (visual only for most homeowners):

• Inspect power cord or junction box: Turn off the breaker. Remove the furnace electrical access cover. Verify that the hot (usually black), neutral (white), and ground (green or bare) wires are securely connected as per the Luxaire wiring diagram on the blower door.
• Check ground connection: Ensure the ground wire is firmly attached to the furnace chassis ground screw.
• Use a plug-in tester (if cord-connected): For furnaces on a receptacle, use a 3-light outlet tester to verify correct polarity and ground.

When to call a pro: If polarity or grounding issues are suspected, an electrician should correct the branch circuit wiring. If wiring is correct but 9 flashes persist, the control board may need replacement.