A42 High
Your boiler has detected an issue with the sensor that measures water temperature as it leaves the unit, which is preventing it from heating correctly.
Technical description: Flow sensor fault – 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 A42 — no call-out fees, no surprises.
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Parts commonly replaced
- NTC Flow Sensor
- Connecting wiring harness
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