Self-Powered Test Lamp and Ohmmeter

Use a self powered test lamp or a ohmmeter to check for continuity. Self powered test lamp is made of a bulb, battery and two leads and is used only on an unpowered circuit. If the leads are touched together, the lamp will go ON. 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 units. Damage to these units 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 at 10 Mega Ohm or higher impedance digital multimeter. When measuring resistance with a digital multimeter, battery negative terminal should be disconnected. Otherwise, there may be incorrect readings. Diodes and solid-state devices in a 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 the readings differ, the solid-state device is affecting the measurement.