L1 High
Your boiler has become too hot or water is not moving through the system properly, causing the unit to shut down for safety.
Technical description: Flow temperature overheat or no water flow
Typical repair cost: £100-£350 (including labour)
DIY fix possible
Check that your radiator valves are fully openEnsure your boiler pressure is between 1.0 and 1.5 barBleed your radiators to remove any trapped air
Protect yourself from future repair bills
A boiler cover plan would cover faults like L1 — no call-out fees, no surprises.
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Parts commonly replaced
- Circulating pump
- Thermistor (Temperature sensor)
- Heat exchanger
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