Boiler display shows E06, boiler shuts down and may restart after cooling

Critical safety: A flue overheat condition can indicate poor venting and carbon monoxide risk. Turn off the boiler and do not operate it until the venting is inspected.

Steps:

• 1. Inspect venting: Check the entire accessible length of the flue pipe for disconnections, crushing, or blockages. At the termination, clear any obstructions.
• 2. Check for soot: Remove the burner access panel and inspect the heat exchanger surfaces visible from the combustion chamber. Heavy soot or black deposits indicate improper combustion and restricted passages.
• 3. Flue sensor connection: Locate the flue temperature sensor (often clipped to the flue or mounted in a well). Ensure its wiring harness is firmly connected and not damaged.
• 4. Reset and test: After clearing any obvious issues, reset the boiler and observe operation. If E06 returns quickly, shut down and call a professional.

Professional service: A licensed technician should check combustion with an analyzer, verify gas pressure, clean the heat exchanger, and replace the flue temperature sensor if it is out of specification.