Checking For Open Circuits/Short Circuits: General

Use a suitable instrument such as a multimeter. An ohmmeter must not be used for testing components containing semi-conductors, e.g. control modules and time delay relays, etc. The power supply to the system being resistance tested must be disconnected because the instrument will apply a low measuring current to the circuit. This will ensure that there is no current already present in the circuit so that a reliable reading can be obtained.