Boiler shows E109 and locks out, often during ignition attempts

Safety first: If you smell gas, do not attempt repairs. Evacuate and contact your gas supplier and a licensed technician. Turn off power and gas before touching gas components.

• Step 1 – Verify gas valves: Confirm the manual gas shutoff valve near the boiler and any upstream valves are fully open.
• Step 2 – Check other gas appliances: See if stoves or other gas appliances operate normally. If not, the building gas supply may be the issue.
• Step 3 – Inspect gas valve wiring: With power off, ensure the gas valve connector is fully seated on the valve and at the PCB.
• Step 4 – Professional pressure test: A licensed technician should measure inlet and manifold gas pressures and test the gas valve coil resistance. Replace the gas valve if it does not open or is out of spec.

Never attempt to disassemble or manually force a gas valve open.