Boiler starts then shuts down with E02; burner lights briefly or not at all.

Safety: Isolate power and gas before opening the boiler casing. Combustion checks must be done by a qualified technician.

• Reset and observe: Reset the CTC boiler and watch the ignition sequence through the sight glass. If the burner lights but E02 appears, the flame is not being detected correctly.
• Check earth/ground: Ensure the boiler has a solid earth connection at the terminal block. Tighten any loose earth screws on the chassis and PCB.
• Inspect ionisation electrode: Remove the ionisation electrode from the burner assembly. Clean light deposits with fine abrasive paper, check the ceramic for cracks, and ensure the tip is correctly positioned in the flame path. Replace if worn or cracked.
• Check ignition/ionisation leads: Inspect high-voltage and ionisation leads for burns, cuts, or loose connections at the PCB and electrode ends. Replace damaged leads.
• PCB flame circuit (technician): If electrodes and wiring are sound, the main control PCB may not be processing the flame signal. Follow CTC diagnostic procedures and replace the control PCB if necessary.