Solid state power switch device comprising a switch unit comprising at least one switch element configured to provide power supply to a load of a vehicle while the switch element is in close state; a switch control unit in communication with the switch unit, said switch control unit being configured to control in open and close state the switch element; wherein the switch control unit comprises a built in self-test module of the switch element, said built in self-test module being configured to control a self-test sequence of the switch element and to check failure or success of the self-test sequence of the switch element such that the switch unit is self-tested; the switch control unit further comprises a current measurement module configured to measure a switch signal value representative of the amplitude of the current passing through the switch element; a reference signal module cooperating with the built in self-test module, and configured to provide a self-test signal threshold value lower than a typical switch signal value representative of the amplitude value of the typical current drawn by the load of the vehicle; a comparator module configured to compare the switch signal value with the self-test signal threshold value, and configured to trigger a driver module such that the switch element toggles in open state of the self-test sequence when the switch signal value is greater than the self-test signal threshold value; the reference signal module is further configured to provide an overload signal threshold value greater than the typical switch signal value; the comparator module is further configured to compare the switch signal value with the overload signal threshold value, and configured to trigger the driver module to control the switch element in open state when the switch signal value is greater than the overload signal threshold value such that the switch unit is protected against overload; the reference signal module comprises a reference voltage providing the overload signal threshold value, and comprises a voltage divider of the reference voltage, and the built in self-test module is configured to enable said voltage divider for setting up the self-test signal threshold value. a switch unit comprising at least one switch element configured to provide power supply to a load of a vehicle while the switch element is in close state; a switch control unit in communication with the switch unit, said switch control unit being configured to control in open and close state the switch element; wherein the switch control unit comprises a built in self-test module of the switch element, said built in self-test module being configured to control a self-test sequence of the switch element and to check failure or success of the self-test sequence of the switch element such that the switch unit is self-tested; the switch control unit further comprises a current measurement module configured to measure a switch signal value representative of the amplitude of the current passing through the switch element; a reference signal module cooperating with the built in self-test module, and configured to provide a self-test signal threshold value lower than a typical switch signal value representative of the amplitude value of the typical current drawn by the load of the vehicle; a comparator module configured to compare the switch signal value with the self-test signal threshold value, and configured to trigger a driver module such that the switch element toggles in open state of the self-test sequence when the switch signal value is greater than the self-test signal threshold value; the reference signal module is further configured to provide an overload signal threshold value greater than the typical switch signal value; the comparator module is further configured to compare the switch signal value with the overload signal threshold value, and configured to trigger the driver module to control the switch element in open state when the switch signal value is greater than the overload signal threshold value such that the switch unit is protected against overload; the reference signal module comprises a reference voltage providing the overload signal threshold value, and comprises a voltage divider of the reference voltage, and the built in self-test module is configured to enable said voltage divider for setting up the self-test signal threshold value.