How to troubleshoot Worcester combi boilers

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How to troubleshoot Worcester combi boilers
Worcester is part of the Bosch Group. (Courtesy of Worcester-Bosch Group)

Worcester is now part of the Bosch Group. Which? members rate Worcester-Bosch as the most popular gas boiler brand, according to Worcester-Bosch themselves. However, sometimes their combi boilers develop problems. Finding out what the problem is -- and what to do to it -- requires a systematic check.

Skill level:
Moderately Easy

Things you need

  • Ruler
  • Hot water bottle

Show MoreHide


    First checks

  1. 1

    Follow the advice of Worcester-Bosch and check whether your combi boiler is displaying a fault code. This might be an EA code. Alternatively, it could be a D5 code.

  2. 2

    Find out what model combi boiler you have. Greenstar gas boilers and the 26 CDi model are prone to frozen condense trap or discharge pipe problems during cold weather.

  3. 3

    Check whether a blue light is flashing. If your combi boiler is a 26 CDi model, look for a flashing red light instead. If all of the above are true, try to reset your boiler.


  1. 1

    Locate the reset button. This is on the boiler control panel. Press the button firmly.

  2. 2

    Hold the button in. Wait ten seconds. Release the button.

  3. 3

    Wait a few minutes. The boiler should reignite. If it does, you have reached a successful outcome to the troubleshooting process.

    Further checks and actions

  1. 1

    Listen for a gurgling noise if your boiler does not fire up. This probably indicates a frozen condense. Check your condense pipe next.

  2. 2

    Check whether the pipe is less than 32 mm in diameter. See whether it is insulated with waterproof lagging. If not, the pipe could be frozen.

  3. 3

    Contact your installer to thaw the pipe. Alternatively, place a hot water bottle against the pipe. However, you should only do this if the pipe is at ground level. It is important not to attempt to thaw a pipe at any other height.

  4. 4

    Reset the boiler using the method above when the pipe has thawed. If this advice does not work or your combi boiler has a different problem, contact Worcester-Bosch customer services (see Resources).

Tips and warnings

  • Exercise great caution when endeavouring to thaw your condense pipe. Worcester-Bosch recommends you get a Worcester Accredited Installer to do the job.

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