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Knowledge document #3696
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The display of the FRITZ!DECT radiator control is frozen

The display of the FRITZ!DECT radiator control, for example FRITZ!DECT 302, is frozen and the last switching state remains active. The radiator control no longer responds when you push a button and the connection to the FRITZ!Box is interrupted.

1 Checking the batteries

FRITZ!DECT radiator controls have energy-saving e-ink displays, like the ones used in e-book readers. Such displays only require current flow when changing the display. If the batteries are removed, or if the batteries are dead or unsuitable, the last indication on the display continues to be shown.

Note:Refer to Wikipedia for more information on how an e-ink display works.

The error usually occurs when unsuitable or dead batteries are used. Proceed as follows:

  1. Remove the batteries from the FRITZ!DECT radiator control.
  2. Push any button on the radiator control for at least 3 seconds. Now the radiator control is reset.
  3. Insert new batteries that are suitable:
    1. Do not use rechargeable batteries. Rechargeable batteries usually have a higher internal resistance and a higher self-discharge rate than disposable batteries and produce lower voltages. This can affect how the radiator control functions and shorten operating time.
    2. Do not use zinc-carbon batteries. Due to their construction, they are not suitable for use in radiator controls.
    3. Use high-quality batteries. Varta Industrial Pro AA, Varta Longlife Max Power AA, GP Super Alkaline LR6, or Duracell Industrial AA are suitable.
  4. Reestablish the DECT connection to the FRITZ!Box.