BoilerFaultCodesYour boiler has detected a communication error or electrical fault that is causing the fan to run at full speed without igniting, meaning your heating and hot water will not work.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Go to section ‘D’: Check continuity across flow microswitch, temperature sensor resistance (approx. 11 kΩ), and fan connections/voltage (230V).
What causes this fault?
This fault occurs when the boiler's internal computer loses track of the water temperature or flow, causing the system to run the fan at high speed as a safety precaution. The most common reason is a sensor that has failed electronically or an electrical component that is no longer sending the correct signals to the main control board.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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 Fan runs at max speed (neon flashing) — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Potterton Performa 24 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.