Furnace will not start; status LED shows 8 red flashes repeating; blower may run continuously.

Safety first: Turn off power before removing access panels. Electrical work should comply with local codes.

Steps to check:

• Verify correct polarity: At the furnace disconnect or junction box, confirm that the hot (usually black) wire is connected to the L (line) terminal and the neutral (white) wire to N. If unsure, have a qualified electrician verify.
• Check furnace grounding: Ensure the green or bare copper ground wire is securely attached to the furnace chassis ground screw. Tighten any loose connections.
• Clean burners and flame sensor: With gas and power off, remove the burner assembly if accessible. Brush off rust and debris with a soft wire brush. Clean the flame sensor rod with fine steel wool. Reinstall burners, ensuring proper alignment and seating.
• Inspect wiring to control board: Look for loose spade connectors or corroded terminals on the integrated furnace control (IFC). Reseat connectors firmly.

If the error persists after cleaning and verifying polarity/ground, a technician should measure flame rectification current and evaluate the control board.