FRITZ!Box 3390 – Service - Knowledge Base

FRITZ!Box 3390 – Service

Constant restarts: Several LEDs flash

The FRITZ!Box constantly restarts (reboots, resets). When this happens, all or several LEDs either flash briefly several times or continuously one after another. Since the FRITZ!Box keeps restarting, you cannot access its user interface. Either particular functions or all of the FRITZ!Box functions are not working properly.

Important:If the FRITZ!Box occasionally restarts, follow the instructions in this guide.

Simply proceed as described below. After each measure, check whether the issue persists.

1 Restarting the FRITZ!Box

  1. Unplug your FRITZ!Box by removing the power cable from the electrical outlet.
  2. Plug it in again after 5 seconds.

    Note:The FRITZ!Box settings will not be deleted when it restarts. The restart will take about 2 minutes. During this time, you cannot access the FRITZ!Box user interface.

2 Using the correct power supply unit

One of the most frequent causes is the use of an unsuitable power supply unit for the FRITZ!Box. For example, you may be using the power supply unit from a different FRITZ!Box model:

3 Disconnecting USB devices for testing purposes

Interference from USB devices connected to the FRITZ!Box may be causing the error. If this is the case, the USB devices may be defective, the devices' system memory or file system may be damaged, or the power required by the USB devices exceeds 500 mA (for example 2.5 inch hard drives, UMTS sticks).
In order to test whether a USB device is causing the issue, proceed step by step as follows:

  1. Remove all USB devices from the FRITZ!Box.
  2. For a sufficient period of time, observe whether the issue reoccurs.
  3. Connect the other USB devices one by one; only connect one USB device at a time.
  4. Check which USB device causes the issue to occur again.
  5. Connect this USB device to the FRITZ!Box by means of a USB hub with its own power supply for testing purposes.

    According to the USB specifications, the power consumption of a USB device may not exceed 500 mA. If the power consumption of the device exceeds this limit, then it must be connected to the FRITZ!Box by means of a USB hub with its own power supply (active USB hub).

  6. For testing purposes, replace this device if the issue also occurs when using it with an active hub.

4 Resetting the FRITZ!Box