1 red flash High
Your boiler has detected that it is getting too hot or that water isn't moving through the system correctly, causing it to shut down for safety.
Technical description: Sensor error, temperature fault or flow fault.
Typical repair cost: £120-250 (including labour)
DIY fix possible
Check that your radiator valves are openEnsure your system water pressure is between 1 and 1.5 bar on the gaugeReset the boiler by turning the selector switch to 'R' for five seconds
Protect yourself from future repair bills
A boiler cover plan would cover faults like 1 red flash — no call-out fees, no surprises.
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Parts commonly replaced
- Temperature Sensor (NTC Thermistor)
- Circulating Pump
- Overheat Thermostat
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