1Multi Function: The car test pen integrates the functions of voltage measurement, bulb load measurement, voltage measurement with bulb load, test at the load of electrical appliances, and power supply polarity display. 2Voltage Measurement Function: The voltage measurement function of the car tester pen is the same as the voltage measurement of the multimeter, the operation is not difficult. 3Bulb Load Measurement: Using a 5W car bulb as the load, the brightness of the bulb can quickly determine the line power supply failure. Compared with the diode test pen, it can show hidden faults such as poor circuit contact and excessive resistance. 4Voltage Measurement with Bulb Load: By measuring the brightness of the light bulb of the electric pen, and in conjunction with the voltmeter function of the electric pen, more accurate voltage measurement can be achieved, thereby improving the fault diagnosis ability. 5Probe Detection: For the load plug, the probe connected to the clip can be used in combination with the probe of the test pen to directly perform load simulation measurement, which is convenient for fault diagnosis. 6Voltage Polarity Display Function: It is more convenient and safer to quickly distinguish the positive and negative poles of the power supply through the red and blue of the light emitting diode.