BoilerFaultCodesYour boiler has likely detected that it is too cold to operate safely or that moisture has affected its internal electronics.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Boiler in very cold environment (less than 5°C) or damp control board.
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the air temperature inside the casing has dropped below 5°C, posing a risk of freezing. It can also be triggered if high levels of moisture or dampness have reached the control board, causing the electronics to misread the temperature. The system shuts down as a safety precaution to prevent structural damage from ice or electrical short circuits.
This fault is almost exclusively seen during extreme winter cold spells or if the boiler is located in an unheated outbuilding or garage.
DIY fix possible
Increase the ambient temperature in the room where the boiler is located to above 5°C.If the area is damp, use a dehumidifier or improve ventilation to dry out the surroundings.Reset the boiler and wait for it to reach a normal operating temperature.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like FAIL POINT F — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Worcester Bosch 25si and 28si is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.