The 75 Relay Circuit Tester from Cal-Van Tools can test an entire circuit from the battery to the component in question. This tool gives technicians the ability to instantly determine the problem within a tested circuit. At the push of a buttom, this tool will identify if a wire, part or relay is defective without the use of a multimeter. The tool also features easily accessible ports for use with other diagnostic tools. The technician can use the tool as a remote control starter in engine work such as compression testing, distributor or cam shaft adjusting, or to run the compressor during an A/C charge.