F Low
Your boiler has sensed a drop in temperature and is temporarily heating itself up to prevent the internal pipes from freezing.
Technical description: The boiler is operating in frost mode
Typical repair cost: £0 (including labour)
DIY fix possible
No action is required; this is a normal safety function.The 'F' will disappear once the boiler reaches a safe temperature.Ensure your external condensate pipe is insulated to prevent it from freezing in cold weather.
Protect yourself from future repair bills
A boiler cover plan would cover faults like F — no call-out fees, no surprises.
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