D1 240 High
Your boiler has detected an electrical fault with the internal sensor that monitors the water returning to the unit, causing it to shut down to prevent damage.
Technical description: The contacts of the boiler return temperature sensor have been short circuited
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 D1 240 — no call-out fees, no surprises.
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Parts commonly replaced
- Return temperature sensor (NTC)
- Wiring harness connector
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