L1 High
Your boiler has shut down because it has detected it is getting too hot or there isn't enough water moving through the system to keep it cool.
Technical description: Flow temperature overheat lockout or no water flow lockout
Typical repair cost: £120-£350 (including labour)
DIY fix possible
Check that your radiator valves are fully openEnsure your boiler pressure is between 1.0 and 1.5 barCheck for any visible leaks in the pipeworkPress the Reset button on the front of the control panel
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 (NTC Sensor)
- Main Heat Exchanger (if blocked)
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