Worcester Bosch Greenstar Boilers
12 fault codes documented
Blue light Fast flash — Hot water not working (central heating OK)
The blue indicator light flashes rapidly, indicating that the boiler is not producing hot water, although the central heating system is functioning normally. This points to an issue with hot water demand or supply.
Blue light Fast flash with 2 pulses — Boiler not responding to any demand
The blue indicator light performs a fast flash with two distinct pulses, meaning the boiler is failing to operate for both central heating and hot water demands. This indicates a general demand or control issue.
Blue light Fast flash with 5 pulses, Reset button Flashing — Ignition lockout
The blue indicator light flashes rapidly with five pulses, and the reset button is also flashing, indicating the boiler has entered an ignition lockout state. This means it tried to ignite multiple times and failed for safety reasons.
Blue light Off, Reset button Flashing — Internal boiler fault
The blue indicator light is off, but the reset button is flashing, indicating a general internal fault within the boiler's control system or major components that prevents operation.
Blue light Off, Reset button Off — No power to control board
The boiler's main blue indicator light and the reset button are both off, indicating a complete lack of power to the control board. This means the boiler cannot operate or respond.
Blue light Slow flash (off then on) — Central heating not working (hot water OK)
The blue indicator light flashes slowly (briefly turning on from an off state), and the central heating system is not operating, though hot water may still be available. This suggests an issue with central heating demand.
Blue light Slow flash (on then off) — Boiler running without central heating demand
The blue indicator light flashes slowly (briefly turning off from an on state), indicating the boiler is operating even when there is no active central heating demand from the external room thermostat or timer. This could lead to unnecessary heating.
Hot water temperature too high — Hot water is too hot
The hot water produced by the boiler is excessively hot, potentially posing a scalding risk and consuming more energy than necessary.
Hot water temperature too low — Hot water is not hot enough
The hot water produced by the boiler is not reaching the desired or expected temperature, making it unsuitable for use.
No on/off indicator light — Boiler appears off or unresponsive
The blue on/off indicator light is not illuminated, and the boiler appears to be off or not receiving a signal to operate, even if mains power is seemingly present.
Desired room temperature not reached — Heating is insufficient
The central heating system is on, but the room does not reach the temperature set on the thermostat or programmer, resulting in a colder environment than desired.
Desired room temperature exceeded — Heating is too strong
The room temperature is significantly higher than the temperature set on the thermostat, leading to overheating and discomfort.