BoilerFaultCodesYour boiler is failing to light the gas flame properly during its first stage of operation.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: ignition
What causes this fault?
This fault occurs when the boiler's control board sends a signal to start the fire, but it fails to detect a stable flame during the initial ignition sequence. The most common reasons are a worn-out spark electrode that can no longer create a spark, or a debris-clogged ignition lead preventing the electrical current from reaching the burner.
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.03 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Glow-worm Flexicom 18sx 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.