Never use a self-powered test light to perform checks for opens or shorts when power is applied to the circuit under test. The test light can be damaged by outside power.
- Isolate the circuit from power and ground.
- Connect the self-powered test light or ohmmeter ground clip to a good ground and probe any easy-to-reach point in the circuit.
- If the light comes on or there is continuity, there is a short somewhere in the circuit.
- To isolate the short, probe a test point at either end of the isolated circuit (the light should be on or the meter should indicate continuity).
- Leave the test light probe engaged and sequentially open connectors or switches, remove parts, etc. until the light goes out or continuity is broken.
- When the light goes out, the short is between the last two circuit components which were opened.