Electrical Component Failure Diagnosis - Open Circuit Diagnosis

Intermittent failures of electrical loads are most often associated with poor quality of terminal connections due to oxidation or loose fasteners. Often, simply wiggling the relevant wiring harness/electrical connector is enough to restore the component to working condition. The simplest way to locate an open circuit is to check the working sections of the circuit for continuity. Disconnect the circuit's power supply and use a meter with a self-contained power source. Connect the meter leads to both ends of the circuit under test (the power supply terminal and a good ground point). If the meter indicates continuity (zero resistance / test lamp lights), the circuit section being tested is intact. Otherwise, there is an open circuit. Switches can be checked for proper operation in the same way.