F.84 High
Your boiler is confused because its temperature sensors are giving conflicting readings or are installed incorrectly, causing the system to shut down for safety.
Technical description: Flow/return temperature sensor fault
Typical repair cost: £100-180 (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 F.84 — no call-out fees, no surprises.
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Parts commonly replaced
- Flow temperature sensor (NTC)
- Return temperature sensor (NTC)
- Sensor wiring harness
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