A02
Immergas
Overheat Lockout
Boiler shows A02, safety thermostat intervention, boiler overheated and shut down.
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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
Blocked primary heat exchanger, Pump failure or air lock, Closed radiator valves causing low flow, Faulty overheat thermostat
How to Fix / Troubleshooting
Safety: Allow the boiler to cool fully before resetting. Do not cover radiators or block ventilation.
- Check system flow: Ensure that enough radiators are open and that thermostatic radiator valves are not all closed.
- Bleed system: Bleed radiators and the boiler's air vent to remove trapped air.
- Check pump: Confirm that the pump runs and that the flow and return pipes heat up evenly. Replace the pump if it is not circulating.
- Reset: Press the reset button. If A02 recurs, an engineer should inspect the primary heat exchanger for blockage and test the overheat thermostat.
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Repair Difficulty
Hard
4/5
Required Part
Circulation Pump
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