Controller displays E01 and the furnace does not start the ignition sequence

Safety first: Turn off power to the Defro furnace at the main switch and isolate it from the electrical supply. Allow the unit to cool completely before opening any panels. Close the fuel (pellet/coal/eco‑pea coal/wood) feed gate if accessible.

Steps to check:

• Remove the front service panel to access the burner and ignition assembly.
• Locate the flame sensor and ignition electrode near the burner head (often mounted on the burner tube or in the combustion chamber door).
• Inspect the flame sensor rod for soot, oxidation, or deformation. Clean it gently with fine emery cloth or a non‑abrasive scouring pad. Do not bend the rod.
• Check the ignition electrode tip for cracks, heavy carbon buildup, or damage. Clean the tip and ceramic insulator. Ensure the electrode gap and position match the Defro service manual (distance to burner head and to ground).
• Inspect the ignition cable for burns, cuts, or loose connections at the control board and ignition transformer.
• Vacuum ash and debris from the burner pot and combustion chamber to ensure proper air/fuel mixture.
• Reassemble, restore power, and attempt a restart. If E01 persists after cleaning and checking connections, the flame sensor or ignition electrode assembly may need replacement.

When to call a technician: If you see cracks in the ceramic insulator, arcing marks on the chassis, or repeated E01 after cleaning, have a qualified Defro service technician test the ignition transformer and control board.