Common Boiler Problems

Worcester Bosch Boilers

As Worcester Accredited Installers throughout Greater London, we specialise in Worcester Bosch central heating boilers and provide expert, experienced advice on installation, repair, servicing and problem-shooting.

Worcester Greenstar Fault Codes

Identifying a possible simple fault with a Worcester Greenstar boiler is made relatively straightforward because of the internal diagnosis system.

COMBI BOILERS – Greenstar 24i Junior

Blue Light IndicatorLockout Reset ButtonFault
OFFOFFNo power at control board
ONOFFNot operating during demand for central heating / hot water / any demand.Operating without live demand at ST10-LR.
Slow FlashFlashing (reset required)Ignition lockout. Flue overheating. Heat exchanger overheating.
Fast flashOFFVolatile lockout
Fast flashFlashing Internal fault
2 pulsesNo lightNot a fault code
5 pulsesNo lightNot a fault code

REGULAR GAS BOILERS – Greenstar 12Ri /15Ri / 18Ri /24Ri


SYSTEM GAS BOILERS – Greenstar 12i /15i /18i /24i

A fault occurring with a Greenstar Ri boiler is identified by the reset button flashing once per second and the mains indicator (blue light), which also will flash but at different speeds according to the type of fault.

Desired room temperature not reached.Thermostatic radiator value or values or room thermostat set too low. Temperature control for CH flow on boiler set too low. Air trapped in heating system.
Desired room temperature exceeded by large amount.Radiators too hot.
Heating stays on for too long.Programmer is incorrectly set.
No on/off indicator light.Brief power failure.
Fast flashBrief power failure.
Hot water temperature too low.Programmer setting. Cylinder thermostat set too low.
Hot water temperature too high.Cylinder thermostat set too high.

Please Note: If your Worcester Bosch boiler model is not featured in the above examples or if a fault remains and cannot be cleared by pressing the reset button, then you will need to call an accredited, qualified Worcester Bosch service engineer, such as BBS Plumbing and Heating, and provide a description of the fault and, if possible the fault flashing sequence from the flashing indicators.

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