Automotive Multi-Tester Probe for Circuit, Continuity, Polarity, and Voltage Testing. Checks Lamps and Electric Motors. Checks Interior and Exterior Lights. Checks Relays and Power Windows. Tests the positive and negative voltage. Polarity test for cables and sockets. This probe is designed to find short circuits and bad earths fast and test power. It can be used to check continuity, polarity, and voltage, as well as lamps, lights, electric motors, relays, and power windows.