Worcester Bosch boilers are a top choice for London homes, valued for their reliability and energy efficiency. Yet, even the best boilers can develop faults. When this happens, your Worcester Bosch boiler will display an error code, helping you identify the issue quickly. Understanding these codes can save you time, money, and stress—especially during those cold London months.

If you’re facing a boiler issue or need expert advice, call 020 8682 2244 or email our team at Maintracts Services Ltd at info@maintracts.co.uk. Our Gas Safe registered engineers are available 24/7 to help you get your heating back on track.

Don’t let a boiler error leave you in the cold. Maintracts Services Ltd has been London’s trusted plumbing and heating expert since 1974. Our experienced team is ready to diagnose and fix any Worcester Bosch boiler error—fast, friendly, and always professional. Call 020 8682 2244 for immediate assistance!

Why Understanding Worcester Bosch Fault Codes Matters

Boiler error codes are more than just numbers—they’re your boiler’s way of telling you what’s wrong. By understanding Worcester Bosch fault codes, you can:

Quickly identify the issue
Decide if it’s a simple fix or needs a professional
Prevent further damage to your heating system
Save on unnecessary repair costs

Worcester Bosch Combi Boiler Error Codes: What To Watch For

Worcester Bosch combi boilers are common in London flats and homes. Here are some of the most frequent error codes and their meanings:

Error Code	Meaning	Common Causes
EA	Flame not detected	Flame sensor malfunction, gas supply issue, ignition fault
A1	Pump stuck or running dry	Low system pressure, air in the system, pump overrun issue
E9	Overheat protection trip	Water temperature too high, faulty NTC thermistor, blocked heat exchanger
C6	Fan speed error	Air pressure switch failure, fan malfunction, flue temperature sensor error
A7	Hot water sensor defect	NTC thermistor fault, wiring issue
FD	Power interrupted	Electrical connection fault, control box issue
9U/9A	Heat control module (HCM) error	Control box or code plug issue
B7	Internal error	Possible control board fault
F0	Gas valve/control box error	Combustion control malfunction
CC	Outdoor sensor defect

If you see any of these codes, try resetting your boiler. If the error persists, it’s best to call a Gas Safe engineer for a safe and thorough repair.

Worcester Bosch Greenstar Error Codes: Model-Specific Issues

The Greenstar range is one of Worcester Bosch’s most popular lines in London. Here are some Greenstar-specific error codes:

C7: Fan not running on start-up (fan or air pressure switch issue)
C1: Fan stopping during operation (possible flue temperature sensor error)
A8: Heat control module invalid (HCM or control box issue)
D4: Primary flow temperature rising too fast (system purge error)
FA: Flame detected after gas valve closed (combustion control malfunction)
F7: Flame detected before burner start (flame sensor malfunction)

If you’re unsure about any code, don’t hesitate to contact Maintracts for expert help.

Worcester Bosch Error Code Meaning: What Should You Do?

When your boiler displays an error code, follow these steps:

Check the manual: Most codes are explained in your boiler’s user manual.
Reset the boiler: Use the boiler reset button. If the code returns, do not keep resetting.
Check system pressure: Low system pressure is a common cause of faults. Top up if needed.
Inspect for obvious issues: Look for leaks, listen for unusual noises, and check the condensate trap/pump.
Call a professional: If the error persists, contact a Gas Safe registered engineer.

When To Call For Boiler Repair In London

Some issues, like topping up pressure or thawing a frozen condensate pipe, can be handled by homeowners. However, for faults involving gas, electrical connection, or persistent boiler lockout, always call a professional. We offer expert boiler repair in London with rapid response across the city.

Common Causes Behind Worcester Bosch Boiler Faults

Understanding the root causes can help prevent future issues:

Air pressure switch failure: Can cause fan and ignition errors.
Flame sensor malfunction: Leads to flame detection errors (EA).
Water pressure sensor: Low system pressure triggers A1 or E119 codes.
Overheat protection trip: Often due to blocked heat exchanger or faulty NTC thermistor.
Pump overrun issue: May cause A1 or circulation faults.
Flue temperature sensor error: Can result in C1 or C6 codes.
Electrical connection fault: May cause FD or F0 errors.
System purge error: D4 code, often after maintenance.
Combustion control malfunction: FA or F0 codes.
NTC thermistor fault: A7, E2, or E9 codes.

Related Boiler Error Codes & Further Reading

If you have a different boiler brand, check out these helpful guides:

Why Choose Maintracts For Worcester Bosch Boiler Repairs In London?

Established since 1974: Decades of experience with all boiler makes and models.
Gas Safe registered engineers: Safety and compliance guaranteed.
24/7 emergency service: We’re always here when you need us.
Transparent pricing: No hidden fees, no call centres.
Comprehensive expertise: Plumbing, heating, electrical, and drainage.

Conclusion: Take Action For A Warm, Safe Home

Don’t let a boiler error disrupt your comfort. Understanding Worcester Bosch boiler error codes empowers you to act quickly and confidently. For expert diagnosis, fast repairs, and friendly service in London, call 020 8682 2244 or email info@maintracts.co.uk. Stay warm, stay safe, and let the professionals handle the rest.

For more information on boiler error codes, maintenance, or to book a repair, contact our trusted team at Maintracts Services Ltd—London’s trusted heating experts since 1974.

Frequently Asked Questions

What do Worcester Bosch boiler error codes mean?

Worcester Bosch boiler error codes are alphanumeric messages displayed on your boiler’s screen to indicate a specific fault or issue. Each code corresponds to a particular problem, such as low water pressure, ignition failure, or sensor faults. Understanding these codes helps you identify the issue and decide whether you can fix it yourself or need a professional.

How do I fix fault code F0 on my Worcester boiler?

The F0 code signals an internal fault, often related to the gas valve, ignition leads, or control box. Try resetting the boiler by pressing and holding the reset button for 3–5 seconds. If the error persists, contact a Gas Safe engineer, as this fault usually requires professional attention.

What does error code EA or EA 229 mean?

EA or EA 229 means the boiler has failed to detect a flame after ignition attempts. This could be due to a gas supply issue, faulty flame sensor, or ignition problem. Check for obvious issues like gas supply and reset the boiler. If the code returns, call a Gas Safe engineer.

How do I resolve an A1 or low water pressure fault?

A1 indicates low system pressure or a pump issue. Check the pressure gauge—if it’s below 1 bar, top up the system using the filling loop. If the pressure drops again or you see leaks, call a professional.

What causes flow sensor faults (E2/D1) and how to fix?

E2 or D1 faults are linked to the flow temperature sensor. Causes include a faulty or dirty sensor, wiring issues, or water flow problems. Cleaning or replacing the sensor may resolve the issue, but persistent faults require an engineer’s help.

What’s the difference between fan errors C6 and C7?

C6 means the fan speed is too high or too low, often due to a faulty fan, air pressure switch, or wiring. C7 means the fan isn’t running at all, usually because of a failed fan or air pressure switch. Both errors require professional diagnosis and repair.

What should I do if I get a flame detection error (EA/F7)?

Flame detection errors (EA or F7) indicate the boiler can’t confirm a flame is present. Causes include a faulty flame sensor, dirty ignition electrode, or flue issues. Try resetting the boiler, but if the error persists, call a Gas Safe engineer.

How do I reset a Worcester Bosch boiler after an error?

Press and hold the reset button on the front control panel for 3–5 seconds until the boiler restarts. If your model doesn’t have a reset button, check the manual for instructions. Only reset once—if the error returns, seek professional help.

When should I call a Gas Safe engineer vs fix it myself?

You can top up pressure, thaw a frozen condensate pipe, or reset the boiler. For gas, electrical, or persistent faults, always call a Gas Safe engineer. Never attempt repairs involving gas or internal components yourself.

How do I prevent condensate pipe freezing issues?

Insulate the condensate pipe, keep your heating on low during cold weather, and ensure the pipe is installed with a fall for proper drainage. If it freezes, thaw it gently with warm (not boiling) water and reset the boiler.