The short version
- Write the code down exactly before you reset anything
- One reset is reasonable, a repeating code is a diagnosis job
- Most Worcester Bosch lockouts protect the appliance rather than indicate it is beyond repair
- Never open the casing or touch gas components yourself
How the code groups work
The pattern is broadly consistent across the Greenstar range. A codes relate to the control and sensing side, C and D codes to fan, flue and airflow, E codes to electrical and sensor faults, and F codes to flame detection and the gas side.
The codes we see most often
These are the ones that come up week to week on Worcester Bosch appliances around Wigan and Leigh, with what each one usually means in practice.
- EA: the boiler has failed to detect a flame. Often ignition or flame sensing, sometimes gas supply. One reset is reasonable, a repeat is a diagnosis job.
- E9: the appliance has overheated and shut down. Usually circulation, so a stuck pump, sludged radiators or a blocked filter rather than the boiler itself.
- C6 or D5: fan speed is outside the expected range. That is a mechanical fault, not something a reset clears for long.
- F7 or F0: an internal sensor or wiring fault. It needs testing rather than guessing.
- A1: low water pressure or pump problem. Check the gauge first; if pressure is fine the pump is the suspect.
The Worcester specific things worth knowing
Greenstar boilers are sensitive to system cleanliness. A large proportion of the overheat and circulation codes we attend on this make trace back to sludge and a neglected magnetic filter rather than a failed component. Their warranties also depend on an annual service being carried out and recorded, so a code appearing on a five year old appliance is worth checking against your service history before parts are discussed.
What you can safely check yourself
There is a small set of checks any homeowner can make before calling out an engineer, and none of them involve the boiler itself.
- Pressure gauge reading against the marked band
- Whether other gas appliances in the house are working, which tells you about supply
- Whether the condensate pipe outside is frozen in cold weather
- Thermostat batteries, timer settings and whether anyone has changed them
Where the line is
Never remove the boiler casing, adjust gas controls or work on any gas component yourself. Those are Gas Safe engineer jobs by law. If you smell gas, call the National Gas Emergency Service on 0800 111 999 and turn the gas off at the meter.
Common questions
Can I reset a Worcester boiler myself?+
One reset after a lockout is reasonable. If the same code returns, stop resetting and get it diagnosed. Repeated resets on a flame fault put the appliance through unnecessary ignition cycles.
What does EA mean on a Worcester boiler?+
It means the boiler tried to fire and did not detect a flame. Causes range from ignition electrodes and the flame sensor to gas supply and condensate blockage, which is why it needs testing rather than swapping parts.
Does a fault code void my warranty?+
No, but a missing annual service can affect a claim. Keep the service records with the boiler documents.
Do you carry Worcester parts?+
Common consumables and frequently failing parts are on the van, so many Worcester faults are fixed on the first visit.
Worcester Bosch fault code showing?
Tell us the model and the exact code and we will bring the likely parts with us rather than diagnosing blind.