Burner lights briefly then shuts down, display shows A02 during operation.

Safety: Switch OFF the heater and isolate gas and power before opening the casing.

• Check gas supply stability: Observe if other gas appliances flicker or go out. If yes, contact your gas provider to check supply pressure.
• Clean main burner: Remove the burner assembly (per Fondital service instructions). Use a soft brush and vacuum to remove dust, rust flakes, or insect debris from burner ports. Do not enlarge or damage the ports.
• Inspect flame sensor: Clean the ionization electrode with a fine abrasive pad. Ensure correct gap and position relative to the burner as specified in the service manual.
• Check wiring: Inspect the wiring harness from the flame sensor and gas valve to the electronic control board for loose plugs, heat damage, or corrosion.
• Professional test: If the problem persists, a technician should measure ionization current and gas valve modulation voltage and replace the gas valve or control board if out of spec.