BoilerFaultCodesYour boiler is failing to detect a flame and has safely shut down to prevent unburned gas from flowing.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: No ionisation signal
What causes this fault?
This fault occurs when the boiler's control system cannot confirm that a flame has successfully lit, leading it to shut down for safety. The most common reasons include a lack of gas reaching the burner, worn-out ignition components that fail to spark, or a dirty internal sensor that can no longer 'see' the flame.
This fault is significantly more common during extreme cold snaps, as the external condensate drainage pipe can freeze and back up, preventing the boiler from lighting.
DIY fix possible
Check if you have credit on your gas meter or if other gas appliances in the house are working.Inspect the white plastic condensate pipe outside for signs of freezing and thaw it with warm water if necessary.Press the 'Reset' button on the boiler fascia for five seconds to see if the system restarts.
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 EA — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Worcester Bosch Greenstar 25 HE Combi 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.