F35 Medium
Your boiler is struggling because the electricity supply from the national grid or your home's wiring is unstable or at the wrong frequency.
Technical description: Faulty mains frequency – electric mains error
Typical repair cost: £100-£350 (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 F35 — no call-out fees, no surprises.
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Parts commonly replaced
- Printed Circuit Board (PCB)
- Surge Protector
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