Identifying your boiler’s fault code in 2024


Unfortunately, just like us, even boilers can have off days! Epecially after a long break from heating your home, problems might arise when your boiler kicks back into gear.

The good news? Most of the time, your boiler can clue you in on what’s wrong, and fixing it doesn’t always need an expert’s touch.

When a boiler malfunctions, it often displays a fault code or error code. However, different models have different codes. At Silverdale Plumbing, we’ve noticed three common ones:

For Worcester boilers, it’s the EA code (or F27 for Vaillant), indicating a blocked condensate pipe. This typically happens during extreme cold snaps when the pipe outside freezes. A quick thaw with hot water or a hairdryer usually does the trick.

Then there’s the U9, A1, or No code (Worcester), F75 (Vaillant), or F1 (Ideal), signaling low water pressure. Topping up your boiler usually resolves this issue, as per the manufacturer’s instructions.

Lastly, there’s the F75 code for Vaillant boilers, suggesting a sensor change. This occurs frequently with these boilers, usually when the sensor fails to register the pump starting.

All your boiler’s fault codes are listed in your manual, serving as a guide for engineers during diagnostics. They’re handy for users too, allowing you to relay the issue when scheduling a visit.

Once you’ve identified the relevant fault error, consult your boiler’s manual or the manufacturer’s website. Both provide insights into the code and offer helpful tips for resolving it.

As accredited installers of top boiler brands like Worcester Bosch, Vaillant, and Ideal, we’ve compiled a list of common fault codes below by brand. Keep reading to see if any apply to you.

And remember, if your boiler has ground to a halt, don’t hesitate. Call Silverdale Plumbing and Heating on 07377861815 today!

Worcester Bosch:

With Worcester Bosch boilers, fault errors usually fall into these categories:

  • Locking errors: A flashing fault code with a warning triangle requires pressing the reset button.
  • Blocking errors: No data is shown, and your boiler stops working. The cause code can be found by pressing the spanner / return button.
  • Cause codes: A 3-digit number displayed when pressing the spanner / return button.
  • Fault errors: Alpha-numeric codes indicating specific errors.

Common Locking Errors include:

  • 9A: Incorrect HCM fitted.
  • 9U: Problem with the code plug.
  • B7: Replace control board.
  • C6: Running too fast / too slow.
  • C7: Fan not running or airflow blocked.
  • D1: Sensor wet or damaged.
  • E2: Flow sensor shorted or damaged.
  • E5: Primary flow sensor overheated.
  • E9: Main heat exchanger overheated.
  • EA: Failure of four ignition attempts.
  • EA: Established flame extinguished.
  • EA: Gas valve coil disconnected.
  • EA: Flame not established during the first 4 seconds of ignition.
  • EA: Pump not detecting water.

Common Blocking Errors include:

  • A1: Little or no water in the system.
  • C1: Fan has stopped.
  • EA: No flame detected.
  • EF: Boiler operating at minimum burner load with a significant flow & return temperature difference.
  • No Code: Airlock or reduced water content.
  • 260: Sensor disconnected or no water content.

Vaillant Fault Error Codes:

  • 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.57: Comfort safety mode 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.
  • F.67: Electronics/flame fault.
  • F.68: Unstable flame signal fault.
  • F.70: Invalid device specific number (DSN).
  • F.71: Flow NTC fault.
  • F.72: Flow/return NTC fault.
  • F.73: Water pressure sensor signal too low.
  • F.74: Water pressure sensor signal outside correct range.
  • F.75: No pressure change detection when starting pump.
  • F.76: Primary heat exchanger overheating.
  • F.77: Flue non-return flap/condensate pump fault.
  • F.78: Interruption to DHW outlet sensor at external controller.
  • F.83: Flow and/or return temperature sensor temperature change fault.
  • F.84: Flow/return temperature sensors incorrectly fitted.
  • F.85: Flow and return temperature sensors incorrectly fitted.
  • F.92: Coding resistor fault.
  • F.93: Gas group fault.

Ideal Boiler Fault Codes:

  • 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.
  • F7: Low Mains Voltage.
  • F9: Unconfigured PCB.
  • L1: Flow Temperature Overheat or No Water Flow.
  • L2: Flame Loss.
  • L5: 5 Boiler Resets in 15 Minutes.
  • L6: False Flame Lockout.

We wish you the best of luck fixing your boiler now you know what all the common boiler fault codes mean! If you are in any doubt though and the boiler has stopped working, please call Silverdale on 07377861815 today!