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Error code: 4A 218

CauseThe supply part of the bi-sensor or supply sensor has measured a central heating water temperature that is higher than 105 °C.



Depending on the type of boiler, it is equipped with a flow sensor or a bi-sensor.

Other symptoms:

    No central heating operation. No hot tap water.


  • Step 1

    Are the service valves open?

  • Step 2

    Is the central heating water pressure at least 1 bar?

  • Step 3

    Has the boiler been properly vented?

  • Step 4

    Are enough radiators, convectors, etc. open?

  • Step 5

    Are the supply, safety and return sensors in order?

  • Step 6

    Check the pump

  • Step 7

    Check the pump control.

  • Step 8

    Is there a central heating system that can completely shut down?

  • Step 9

    Is there a bypass or open distributor in the central heating system?

  • Step 10

    Is the bypass or open distributor OK?

This malfunction requires the help of a professional

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