Boiler does not ignite, burner does not start, display shows E01 shortly after a heat demand.

Safety first: Turn off the boiler main switch and close the gas shut-off valve before opening any covers. Wait for all components to cool down.

• Check gas supply: Ensure the main gas valve to the Klimosz boiler is open and that other gas appliances in the house work. If there is no gas supply, contact your gas provider.
• Reset the boiler: Use the reset button on the Klimosz control panel (refer to your model’s manual). If E01 reappears immediately, continue with checks.
• Inspect burner and nozzle: Remove the burner cover. Check the burner head and gas nozzle for soot, rust, or debris. Clean gently with a soft brush and compressed air. Do not enlarge the nozzle orifices.
• Check ionization electrode: Inspect the ionization/flame electrode for cracks, heavy oxidation, or incorrect distance to the burner surface. Clean with fine sandpaper and ensure the ceramic insulator is intact. Re-seat the electrode firmly in its bracket.
• Inspect ignition cables and transformer: Look for damaged insulation, loose connectors, or burn marks on the ignition transformer and high-voltage cables. Reseat all connectors on the ignition module.
• Test again: Restore gas and power, then call for heat. If E01 persists after cleaning and visual checks, the ignition module or gas valve may require replacement by a qualified Klimosz technician.