How much does it cost to fix Keston error code B 65?

Typical repair cost for the Keston B 65 fault is £150-350 including labour.

B 65 High

Keston B 65 Fault Code

Q: What does the Keston B 65 fault code mean?

Your boiler is temporarily paused because it is waiting for its internal air extraction system to spin up correctly before it safely ignites.

Also written as B65 — same fault.

The Keston B 65 fault code means: your boiler is temporarily paused because it is waiting for its internal air extraction system to spin up correctly before it safely ignites.. It appears on 3 Keston models in our database.

Technical description: Waiting for fan to start

Typical repair cost £150-350 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Keston models that show the B 65 fault code

Click a model for the full fault code list and model-specific repair notes.

C40 Repair: £180-350
C55 Repair: £150-350
C90 / C110 Repair: £150-300

Source

Keston B 65 fault code information on this page is sourced and cross-checked against the official Keston service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026