A03 High
Your boiler has likely overheated because water isn't moving through the pipes correctly or there is too much trapped air in the system.
Technical description: Heating sensor damaged, no water circulation or air in system
Typical repair cost: £100-280 (including labour)
DIY fix possible
Check that your system pressure is between 1 and 1.5 barBleed your radiators to remove any trapped airEnsure all radiator valves and isolation valves are fully openReset the boiler using the reset button
Protect yourself from future repair bills
A boiler cover plan would cover faults like A03 — no call-out fees, no surprises.
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Parts commonly replaced
- Circulation Pump
- Heating Temperature Sensor (NTC)
- Limit Thermostat
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