A2
Worcester Bosch
Overheat Thermostat Tripped
Boiler displays A2 and will not run, often after overheating events.
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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
Insufficient circulation, Blocked heat exchanger, Faulty pump, Airlock in primary circuit
How to Fix / Troubleshooting
Safety first: Allow the boiler to cool completely. Do not bypass safety devices.
- Check radiators and valves: Ensure that enough radiators are open and that thermostatic radiator valves (TRVs) are not all closed, which can restrict flow.
- Bleed system: Remove air from radiators and any high points. Top up pressure as needed.
- Reset overheat stat (engineer level): Some Worcester Bosch models have a manual reset overheat thermostat inside the casing. A qualified engineer should reset this and investigate the cause of overheating.
- Investigate pump and blockages: The engineer should verify pump operation and check for blockages in the primary heat exchanger or pipework.
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Repair Difficulty
Hard
4/5
Required Part
Overheat Thermostat
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