F35 Medium
Your boiler has detected an issue with the quality of the electricity coming into your home, meaning the power supply is not stable enough for it to operate safely.
Technical description: Irregular mains frequency – electric supply problem
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
- PCB (Main Control Board)
- Surge Protector
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