104 High
Your boiler has detected that water is not circulating correctly through the system, causing it to shut down for safety.
Technical description: Flow check failed
Typical repair cost: £150-350 (including labour)
DIY fix possible
Check that the central heating pressure gauge is between 1 and 1.5 barEnsure all radiator valves are fully openCheck that the boiler isolation valves underneath the unit are switched to the open positionReset the boiler using the 'R' or Reset button
Protect yourself from future repair bills
A boiler cover plan would cover faults like 104 — no call-out fees, no surprises.
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Parts commonly replaced
- Circulation Pump
- Water Pressure Sensor
- Main Heat Exchanger (Flushing)
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