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Last updated on February 15th, 2024 at 05:58 pm

If your boiler shows an error code you should consult the manufacturers manual to identify the problem, or contact a boiler engineer to repair the persisting issue. Common boiler error codes include ‘F75’ on a Vaillant boiler indicating a flow sensor issue, ‘E133’ signaling failed ignition attempts or ‘EA’ flashing up as a blocked condensate pipe.

Modern boilers are equipped with diagnostic systems that monitor their operation and can detect various issues that may arise, from ignition failures to airflow blockages. When a problem is detected, boilers often display error codes or fault codes to help homeowners identify and address the issue promptly. 

Understanding what these codes mean and how to respond to them can help you troubleshoot your boiler effectively and prevent needing boiler repair.

In this guide, we’ll explore common boiler error codes and provide guidance on what to do if your boiler displays one.


What Do I Do If My Boiler Shows An Error Code? 


The first step when your boiler displays an error code is to consult the manufacturer’s manual. The manual typically contains a list of error codes along with explanations of their meanings and recommended actions to resolve them. Refer to the manual to identify the specific error code displayed on your boiler.

Error codes can indicate a wide range of issues, including problems with the ignition system, sensors, water pressure or internal components. Take note of the error code and any accompanying messages or symbols displayed on the boiler’s control panel.

If the issue cannot be solved with some quick troubleshooting, you should find a boiler repair specialist near you to help fix the problem, or offer you a quote for a new boiler installation


Popular Boiler Brand Error Codes


The tables below provide a quick reference for understanding common error codes for each boiler brand, helping homeowners troubleshoot issues more efficiently. Remember, if you encounter an error code on your boiler that you’re unsure about, consult the manufacturer’s manual or contact a qualified engineer for assistance.


Worcester Bosch Boiler Fault Codes

Error Code Description
9A Incorrect HCM fitted
9U Problem with the code plug (faulty or not connected)
B7 Replace control board
C6 Running too fast / Running too slow
C7 Fan not running / Airflow blocked
D1 Sensor wet or damaged (boiler blocks for 300 seconds)
E2 Flow sensor shorted or damaged
E5 Primary flow sensor overheated
E9 Main heat exchanger overheated
EA Failure of four ignition attempts


Vaillant Boiler Fault Codes

Error Code Description
F.49 eBUS fault
F.52 Mass flow sensor connection fault
F.53 Mass flow sensor fault
F.54 Gas pressure fault
F.56 Mass flow sensor regulation fault
F.61 Gas valve regulation fault
F.62 Gas valve switch-off delay fault
F.63 EEPROM error
F.64 Electronics/NTC fault
F.65 Electronic temperature fault


Ideal Boiler Fault Codes

Error Code Description
C0 BCC Activation Fault
C2 BCC Fault
F1 Low Water Pressure
F2 Flame Loss
F3 Fan Fault
F4 Flow Thermistor
F5 Return Thermistor
F6 Outside Sensor Failure


How Should I Respond to Boiler Error Codes?


  • Restart the Boiler: In some cases, simply restarting the boiler may clear the error code and reset the system. Turn off the boiler, wait a few minutes, and then turn it back on. Monitor the boiler to see if the error code reappears.
  • Check for Obstructions: Inspect the boiler’s air intake and exhaust vents for any obstructions or blockages. Clearing these obstructions can improve airflow to the boiler and help resolve certain error codes related to combustion or ventilation issues.
  • Repressurise the System: If the error code indicates a low water pressure condition, follow the manufacturer’s instructions to repressurise the boiler system. This typically involves using the boiler’s filling loop to add water until the pressure gauge reaches the recommended level.
  • Inspect Ignition Components: If the error code relates to an ignition fault, such as E110, inspect the ignition components for signs of wear or damage. Clean or replace the electrodes, ignition lead, or other components as needed to restore proper ignition.
  • Check Gas Supply: If the error code indicates a gas supply issue, such as E133, check that the gas supply valve is fully open and that there are no issues with the gas supply to the property. If necessary, contact your gas supplier for assistance.
  • Reset the Boiler: Some error codes may require manually resetting the boiler to clear the fault condition. Refer to the manufacturer’s instructions for your specific boiler model to learn how to perform a manual reset.
  • Contact a Qualified Engineer: If you’re unable to resolve the error code on your own or if the error code persists after troubleshooting, it’s advisable to contact a Gas Safe registered boiler engineer for further assistance. They will have the expertise and tools necessary to diagnose and repair the underlying issue safely.


If In Doubt, Schedule A Boiler Repair

By understanding the meanings of common error codes and following the appropriate steps to troubleshoot them, you can often resolve minor boiler issues on your own. However, if you’re unsure how to proceed or if the error code persists, don’t hesitate to contact a qualified boiler engineer for professional boiler repair or replacement boiler installation.

Warmable can help you find a boiler repair engineer, wherever in the UK you are located

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