A13
Fondital Flue Gas Overtemperature / Safety Cut-out

Boiler locks out with A13, often after long operation, casing may feel unusually warm

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Partially blocked Fondital flue or terminal, Incorrect flue installation causing recirculation, Faulty flue gas temperature sensor, Fan not reaching correct speed

How to Fix / Troubleshooting

Safety: Turn off the boiler and ventilate the room. Do not operate the boiler until the flue system has been checked.

User checks:

  • External flue: Visually inspect the outside terminal for obstructions or signs of flue gases staining the wall.
  • Reset: After cooling, reset once. If A13 returns, stop using the boiler.

Technician actions:

  • Inspect the entire Fondital flue system for blockages, incorrect joints, or recirculation issues.
  • Test and replace the flue gas temperature sensor if readings are incorrect.
  • Check fan speed and modulation; replace the fan if underperforming.
  • Verify combustion settings with a flue gas analyser and adjust gas valve if needed.
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Repair Difficulty

Professional Required 5/5

Required Part

Flue Gas Temperature Sensor
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