A device for testing multi-wire harnesses, printed wiring board assemblies and card cages for wiring faults. The device comprises power and logic circuits in a housing, a fault indicator panel, a resistance balance circuit and a low voltage wiring test array. The wire harness is connected with both ends of the wires to sets of terminals on the wiring test array. In testing a wire harness, the operator grasps two probes which are attached to the resistance balance circuit and wipes them on the terminals of the test array. For test of printed wiring board assemblies or card cages, only one probe is required to contact the terminals on the test array. This action causes the resistance balance circuit to combine with the wiring test array segment and a wiring harness wire to form a voltage divider circuit which outputs voltage signals related to the wiring status. The device logic processes these signals and causes any fault indication to illuminate on the indicator panel. The device is light, and portable and offers the advantages of low cost, ease of use, safety and simplicity.