F43 High
Your boiler has detected a problem with the sensor that monitors internal water temperature, preventing the system from heating up correctly.
Technical description: Flow sensor fault – sensor damaged – sensor needs changing
Typical repair cost: £90-160 (including labour)
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Protect yourself from future repair bills
A boiler cover plan would cover faults like F43 — no call-out fees, no surprises.
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Parts commonly replaced
- NTC Temperature Flow Sensor
- Wiring harness
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