703 Medium
Your boiler is struggling to monitor the temperature for one of your heating zones, which may cause that specific area of your home to not heat correctly.
Technical description: Send sensor defective (Zone 3)
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 703 — no call-out fees, no surprises.
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Parts commonly replaced
- Flow temperature sensor (NTC)
- Sensor wiring harness
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