F.33 High
Your boiler has sensed it is too cold and the fan is stuck trying to protect the internal pipes from freezing.
Technical description: Fan frost protection function active – air pressure switch fault
Typical repair cost: £120-250 (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 F.33 — no call-out fees, no surprises.
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Parts commonly replaced
- Air pressure switch
- Fan assembly
- Venturi tube
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