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Knowledge document #3696
FRITZ!DECT 302
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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 reacts when you push a button and the connection to the FRITZ!Box is interrupted.

1 How the display works

FRITZ!DECT radiator controls have energy-saving e-paper displays like the ones used in e-book readers. E-paper displays only require a current flow when changing the display. When the batteries are removed or if they are dead or unsuitable, the last indication remains on the display.

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

2 Testing the boost function

To rule out that vacation switching or the "heating ended" function is configured, check whether the FRITZ!DECT radiator control's boost function works:

  1. Push the (boost function) button on the radiator control. Now the radiator control heats at full power for the amount of time displayed.
  2. If the radiator control starts the boost function, follow the steps in our guide FRITZ!DECT radiator control does not react when button is pushed.
    • If the boost function is not initiated on the radiator control, continue with the next section.

After testing the boost function, you can end the function again before the time is up by pushing the button.

3 Changing the batteries and resetting the radiator control

  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. Varta Industrial Pro AA, Varta Longlife Max Power AA, GP Super Alkaline LR6, or Duracell Industrial AA are suitable.
    2. Do not use rechargeable batteries. Rechargeable batteries usually have a higher internal resistance and a higher self-discharge rate than disposable batteries and often produce lower voltages. This can affect how the radiator control functions and shorten operating time.
    3. Do not use zinc-carbon batteries. Due to their construction, they are not suitable for use in radiator controls.

4 Re-registering FRITZ!DECT radiator controls

  1. Register the FRITZ!DECT radiator control with the FRITZ!Box.
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