Worcester Boiler Fault Codes – What They Mean & What To Do
Worcester boilers use fault codes to explain why the boiler has stopped working or locked out. These codes help engineers diagnose faults quickly, but for homeowners they can be confusing, especially when the heating or hot water suddenly stops.
This guide explains the most common Worcester boiler fault codes, what they usually mean in real-world situations, what you can safely check yourself, and when the fault needs a Gas Safe engineer.
This page focuses on understanding the fault logic, not guesswork or unsafe DIY repairs.
How Worcester boiler fault codes work
Modern Worcester boilers constantly monitor temperature, pressure, airflow, ignition and water circulation.
If something moves outside safe limits, the boiler will:
• Display a fault code
• Flash a blue or red light
• Shut down to prevent damage or unsafe operation
Some faults are temporary conditions, such as low pressure, while others indicate component or system problems that won’t be fixed by repeatedly pressing the reset button.
Common Worcester Greenstar fault codes explained
Below are the fault codes we most commonly see during real call-outs.
EA227 – Ignition Failure or Flame Loss
What it means
The boiler has attempted to ignite but cannot establish or maintain a stable flame.
Although frozen condensate pipes are a common cause during winter, EA227 is a general ignition fault and can have several underlying causes.
Common real causes
• Frozen condensate pipe
• Interrupted gas supply
• Faulty ignition electrode
• Flame sensing electrode issues
• Gas valve faults
• Water ingress around burner components
• Condensate backing up into the combustion chamber
• Low gas pressure
What you can safely check
• Other gas appliances working normally
• External condensate pipe frozen during cold weather
• Try one reset only
When to stop
If EA227 repeatedly returns, the fault requires investigation. Repeated resets may temporarily restore heating, but they will not cure ignition, gas valve or flame detection problems.
Why EA227 is one of the most common Worcester faults
EA227 is one of the most common Worcester boiler faults seen by engineers. Although many homeowners assume the boiler itself has failed, the underlying cause can range from a frozen condensate pipe to ignition electrodes, gas supply problems or water ingress affecting burner components.
Simply clearing the fault code does not fix the cause.
EA – No Flame Detected
What it means
The boiler attempted to ignite but could not establish or detect a flame.
Common real causes
• Gas supply interruption
• Frozen condensate pipe during cold weather
• Faulty ignition electrode
• Flame sensing issues
• Gas valve faults
What you can safely check
• Other gas appliances working
• Frozen external condensate pipe
• Try one reset only
When to stop
If the fault returns after a reset, the boiler needs investigating rather than repeatedly resetting.
224 – No Ionisation Current After Ignition
What it means
The burner has attempted to light, but the boiler cannot confirm a stable flame.
Common real causes
• Ignition electrode faults
• Flame sensing problems
• Low gas pressure
• Gas valve issues
• Water ingress around burner components
What you can safely check
• Other gas appliances operating normally
• One reset only
When to stop
Repeated 224 faults normally require professional diagnosis.
228 – Flame Detected When No Flame Should Be Present
What it means
The boiler is detecting a flame signal when combustion should not be taking place.
Common real causes
• Faulty flame electrode
• Moisture affecting ignition components
• Wiring faults
• PCB problems
What you can safely check
Nothing safely user-serviceable.
When to stop
Persistent 228 faults require investigation.
E9 – Overheat Protection Activated
What it means
The boiler has detected excessive temperatures and shut down to protect itself.
Common real causes
• Sludge restricting circulation
• Blocked heat exchanger
• Pump faults
• Closed radiator valves
What you can safely check
• Radiator valves open
• Correct system pressure
When to stop
Repeated E9 faults usually point towards circulation or heat transfer problems.
A1 / 281 – Poor Water Circulation
What it means
The boiler has detected inadequate circulation through the heating system.
Common real causes
• Low pressure
• Air trapped within the system
• Sludge and debris
• Pump issues
• Restricted flow
What you can safely check
• Pressure around 1.0–1.5 bar when cold
• Radiator valves fully open
When to stop
If the fault keeps returning, the system needs investigating rather than continually topping up and resetting.
101 / 102 – Overheating or Poor Heat Dissipation
What it means
The boiler temperature is rising too quickly.
Common real causes
• Restricted circulation
• Sludge build-up
• Pump efficiency problems
• Heat exchanger issues
What you can safely check
• Radiators heating evenly
• System pressure normal
When to stop
These faults often point to wider system problems rather than a fault inside the boiler itself.
C6 / C7 – Fan or Airflow Fault
What it means
The boiler cannot confirm safe airflow for combustion.
Common real causes
• Fan motor faults
• Wiring problems
• Flue restrictions
• Air pressure sensing faults
What you can safely check
Nothing safely user-serviceable.
When to stop
Airflow faults are safety-critical and require professional diagnosis.
D1 – Temperature or Flow Sensor Fault
What it means
The boiler is receiving incorrect information from one of its sensors.
Common real causes
• Faulty sensor
• Wiring problems
• PCB faults
What you can safely check
Nothing safely user-serviceable.
When to stop
Persistent D1 faults should be investigated professionally.
Note: On some newer Worcester Greenstar boilers, loose or incorrectly seated temperature sensors can cause intermittent hot water problems and recurring lockouts.
Blue Light Flashing (No Code Displayed)
What it means
The boiler is attempting ignition or cycling without successfully firing.
Common real causes
• Low pressure
• Ignition problems
• Sensor delays
• Temporary lockout conditions
What you can safely check
• Pressure gauge around 1.0–1.5 bar
• One reset only
When to stop
Repeated flashing without ignition often develops into a lockout fault.
Which Worcester boilers use these fault codes?
These fault codes are commonly found on:
• Worcester Greenstar 2000
• Worcester Greenstar 4000
• Worcester Greenstar 8000 Style
• Greenstar CDi Compact
• Greenstar i
• Greenstar Si Compact
• Worcester combi boilers
• Worcester system boilers
Although the displays and code formats vary between models, the fault logic remains very similar across most modern Worcester boilers.
Why Worcester fault codes often return after resetting
A reset only clears the symptom, not the cause.
In real-world call-outs, recurring faults are commonly caused by:
• Sludge and circulation issues
• Pressure loss from hidden leaks
• Worn ignition electrodes
• Gas supply problems
• PCB or Sensor failures
• Water ingress around burner components
Repeated resets may temporarily restore heating or hot water, but they rarely fix the underlying fault.
When a Worcester fault code needs an engineer
You should stop resetting and arrange a repair if:
• The same fault keeps returning
• Multiple codes appear
• The boiler repeatedly locks out
• Heating or hot water becomes unreliable
• The boiler overheats
Modern boilers are designed to protect themselves. Fault codes are warnings, not suggestions.
Need a wider explanation of boiler fault codes?
If you want to understand how boiler fault codes work across all brands, what is safe to check, and when a fault becomes serious, see our main guide below.
→ Boiler Fault Codes Explained – What They Mean & When to Worry