BoilerFaultCodesYour boiler is pausing during its startup sequence while it waits for a signal that the fire has safely lit.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Fan and pump running
What causes this fault?
This status occurs when the boiler's internal computer is waiting for the flame sensors to confirm the burner has successfully lit. It usually signals a breakdown in communication between the ignition components and the control board, often caused by worn-out spark electrodes or a faulty gas valve failing to release fuel. If the boiler cannot confirm a safe flame after several attempts, it will eventually stop trying and display a full fault code.
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 S.5 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
Affiliate links — we may earn a commission at no extra cost to you.