A robotic work tool system (200), comprising a charging station (210), a boundary wire (250), a signal generator (240) for generating and transmitting a signal through said boundary wire (250) for demarcating a work area (205) and for generating a magnetic field (265) for guiding a robotic work tool (100) to said charging station (210), said robotic work tool (100) being configured to detect a magnetic field strength of the magnetic field (265) in the work area (205), direct itself towards an increasing magnetic field strength, determine that the robotic work tool (100) is unable to reach the charging station (210), inform the robotic work tool system (200) accordingly, whereby the robotic work tool system (200) is configured to adapt a current level of the signal generating the magnetic field (365).
