worcester fault diagnostics

Worcester Greenstar 12i System — Heat exchanger overheat

The Worcester Greenstar 12i System displaying a "Heat exchanger overheat" fault code indicates the boiler's safety systems have activated due to excessively high temperatures within the heat exchanger. This is a critical safety lockout designed to prevent damage to the appliance. Common causes include poor water circulation, a blocked heat exchanger (often due to limescale or sludge), airlocks, or a faulty pump. The intermittent nature suggests a developing issue rather than a sudden component failure. The pressure reading of 1.5 bar is within the normal operating range, so low pressure is unlikely to be the primary cause.

Published 3rd June 2026

worcester greenstar cdi

The Worcester Greenstar CDi is a condensing combination boiler. The symptom of 'won't come up to heat' without a specific fault code can indicate several issues, ranging from basic user settings to component failures. Common causes include low system pressure, issues with the gas supply, condensate blockages, or problems with key components like the fan, ignition electrodes, or PCB. There are no specific service bulletins for a general 'no heat' fault, but manufacturer documentation and reputable trade sources highlight these common failure modes.

Published 20th April 2026

Worcester Greenstar 12i System — Ignition lockout

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.

Published 8th April 2026