Self-Powered Test Lamp and Ohmmeter

Use a self-powered test lamp or an ohmmeter to check for continuity. A self-powered test lamp is made of a bulb, battery and two leads. That will light a lamp when touched together. Prior to checking the points, first disconnect the battery ground cable or remove the fuse which feeds the circuit you are working on.


CAUTION: Never use a self-powered test lamp on circuits that contain solid state modules. Damage to these modules may result.

An ohmmeter can be used in place of a self-powered test lamp. The ohmmeter shows how much resistance there is between two points along a circuit. Low resistance means good continuity.





Circuits which include any solid-state devices should be tested only with a 10-megaohm or higher impedance digital multimeter. When measuring resistance with a digital multimeter, the battery negative terminal should be disconnected. Otherwise, there may incorrect readings. Diodes and solid-state devices in a be circuit can make an ohmmeter give a false reading. To find out if a component is affecting a measurement, take one reading, reverse the leads and take a second reading. If different the solid-state device is affecting the measurement.