Furnace locks out shortly after ignition, flame appears unstable or goes out repeatedly

Safety first: Disconnect power and close the gas valve before servicing. Allow the combustion chamber to cool.

• Inspect burner injectors: Remove the burner cover. Check the gas injectors (nozzles) for dirt or corrosion. Clean gently with a soft brush and compressed air. Do not use sharp tools that can deform the orifices.
• Check flame sensor wiring: Locate the flame sensor/ionization probe lead. Ensure the connector is tight at both the probe and the control board. Look for signs of heat damage or brittle insulation. Replace the lead if damaged.
• Verify furnace ground: Confirm the green/yellow ground wire is firmly attached to the furnace chassis and the supply ground. Tighten any loose screws and remove rust or paint under the ground lug.
• Ventilation and combustion air: Make sure the combustion air openings and room ventilation grilles are not blocked. Poor air supply can cause flame instability.
• Test run: Restore gas and power. Reset the furnace and observe the flame through the inspection window. A stable blue flame should remain on. If the error returns, gas pressure or the control board may need professional adjustment or replacement.

Warning: Gas pressure checks and adjustments must be performed only by a certified technician with a manometer and Roca specifications.