Worcester Greenstar 12i System fault Ignition lockout: The boiler has stopped working, and we have no heating or hot water
Published 8 April 2026 · Generated by BoilerTag's diagnostic AI from an engineer's real-world submission
One of 13 real-world fault checklists on BoilerTag, across 5 boiler makes.
Most likely cause
The Worcester Greenstar 12i System displaying an 'Ignition lockout' fault indicates that the boiler has attempted to ignite but failed to detect a flame, leading to a safety shutdown. This is a protective mechanism to prevent unsafe operation. The boiler will not restart until the underlying fault is identified and resolved, and the boiler is manually reset. Repeatedly resetting the boiler without addressing the cause can lead to further damage to components like the PCB and ignition parts.
The engineer's report
A gas engineer submitted this case through BoilerTag's free fault diagnostic tool, working on a Worcester Greenstar 12i System displaying fault code Ignition lockout. They described the behaviour they were seeing on site as follows:
“The boiler has stopped working, and we have no heating or hot water. The display panel shows 'Ignition lockout' and it keeps beeping. It tries to start up, makes a clicking noise, but then stops and displays the same message.”
Before requesting the AI diagnostic, the engineer had already worked through the following checks:
“I've tried pressing the reset button a few times, but it just comes back with the same fault. I also checked the pressure gauge, and it looks normal. I had a quick look at the white pipe outside, and it doesn't seem to be blocked or frozen.”
BoilerTag's diagnostic AI then cross-checked manufacturer documentation and common trade knowledge to produce the prioritised checklist below.
Diagnostic checklist
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Commonly failed parts
- Ignition electrodes/leads (if found to be worn or dirty)
- Gas valve solenoids (if resistance is out of specification)
- Heat cell gasket (red seal) and gas tube (often available as a kit, common failure points for intermittent lockouts)
More Worcester fault codes
Sources
The AI cross-checked the following manufacturer and trade sources while producing this checklist.
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