Boiler will not start; control shows E01 and burner never lights

Safety first: Turn off electrical power to the boiler at the service switch and close the gas shutoff valve before removing any panels. If you ever smell gas, evacuate and contact your gas supplier or a licensed technician immediately.

Step-by-step checks:

• Verify gas supply: Confirm the manual gas shutoff valve to the Dettson boiler is fully open. Check that other gas appliances in the home work. If not, contact the gas utility.
• Reset the boiler: Restore power, then press the boiler reset button (or follow the reset procedure in the Dettson manual). Observe if the boiler attempts ignition (you should hear the fan and clicking from the igniter).
• Inspect ignition electrode: With power OFF, remove the burner access panel. Locate the Dettson ignition electrode assembly. Check for cracked porcelain, broken wires, or heavy soot. Clean the tip gently with fine emery cloth and ensure the gap and position match the service manual.
• Check flame sensor: Many Dettson boilers use a combined igniter/flame rod or a separate flame sensor. Clean the rod with fine steel wool to remove oxidation. Ensure the wire connection is tight at the control board.
• Inspect wiring and ground: Confirm all low-voltage and high-voltage connections between the ignition control module and the burner assembly are secure. Verify the boiler chassis is properly grounded.
• If E01 persists: The Dettson ignition control module or gas valve may be defective. Do not attempt to open or repair these components. Contact a qualified boiler technician to test gas pressure, ignition current, and replace parts as needed.