Abstract: An electrical circuit testing system for troubleshooting automotive electrical circuitry includes an automotive diagnostic unit that is selectively and electrically coupled to an electrical circuit in a vehicle. A housing is provided and a pair of inputs is each coupled to the housing. Each of the inputs is selectively placed in electrical communication with an electrical circuit in a vehicle. A voltmeter is coupled to the housing and the voltmeter is electrically coupled to the processor to detect voltage in the electrical circuit in the vehicle. A load circuit is positioned in the housing and the load circuit is electrically coupled to the processor. The load circuit selectively places an electrical load on the electrical circuit in the vehicle when the inputs are in electrical communication with the electrical circuit. In this way problems in the electrical circuit in the vehicle may be diagnosed.