D.34 High
Your boiler is struggling to accurately measure how fast its internal fan is spinning, which is preventing the system from heating correctly.
Technical description: Fan speed actual value
Typical repair cost: £250-480 (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 D.34 — no call-out fees, no surprises.
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Parts commonly replaced
- Extraction fan
- Wiring harness
- Main PCB
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