Safety: Switch off the furnace and disconnect from mains. Allow the combustion chamber to cool fully.

Open the burner access door and inspect the burner pot/grate for clinker, slag, or ash blocking the air holes. Remove deposits with a metal scraper and vacuum.
Check the screw feeder (auger) for bridging or compacted fuel in the hopper. Break up any clumps and ensure pellets/coal move freely.
Verify that the combustion fan (exhaust/induced draft fan) spins freely and is not obstructed by ash or debris. Clean the fan blades and housing.
Inspect the flame sensor for soot buildup and clean as described for E01.
In the Defro controller menu, confirm that combustion air and fuel feed settings match the fuel type recommended by Defro. Do not arbitrarily increase feed rate without adjusting air.
Restart the furnace and observe the flame through the inspection window. If the flame is weak, pulsing, or goes out repeatedly, further adjustment or component replacement is needed.

Call a technician if: The E02 repeats after cleaning and basic checks, or if the combustion fan does not start or runs erratically.

E02 displayed and furnace shuts down shortly after ignition attempt

Possible Causes