815 W/B High
Your boiler's temperature sensors are receiving conflicting or incorrect readings, causing the system to stop working correctly to protect itself.
Technical description: Low loss header temperature sensor faulty – check the sensor port or check the differential sensor for incorrect installation position or breakage
Typical repair cost: £120-190 (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 815 W/B — no call-out fees, no surprises.
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Parts commonly replaced
- Low loss header temperature sensor
- NTC thermistor
- Wiring harness
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