Check A Battery Or Ignition Voltage Circuit With A 12-Volt Test Light

CHECK A BATTERY OR IGNITION VOLTAGE CIRCUIT WITH A 12-VOLT TEST LIGHT





1. Turn the ignition off.
2. Disconnect the wire harness connector of the component that is receiving the voltage.

NOTE: Check connectors - Clean/repair as necessary.

3. At this time, leave all in-line connectors connected.

NOTE: Before inspecting any circuits, first test the 12-volt test light. Connect the 12-volt test light to battery ground or to any other known good ground. Touch the lead of the test light to Battery +. If the test light is good, it should illuminate brightly.

4. Connect the 12-volt test light to a known good ground.
5. Use the test light lead to carefully probe the Battery or Ignition Voltage circuit in the harness connector.
6. First check with the ignition off, next check with the ignition on, and lastly check while cranking the engine.

Does the test light illuminate brightly?

Yes

- The circuit is not open at this time or the condition that originally caused the open may not be present at this time. Continue to monitor the test light and wiggle the wire harness and connectors to check for an intermittent open or excessive resistance condition.
- Use the wiring application as a guide to trace the circuits and look for any in-line connectors where the open could occur intermittently.
- Look for any chafed, pierced, pinched, or partially broken wires.
- Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related wire harness connectors.
- Perform any Technical Service Bulletins (TSBs) that may apply.

No

- Repair the open in the circuit. Use the wiring application as a guide to trace the circuit and look for any in-line connectors where the short could occur.
- One way to help isolate the open is to disconnect any in-line connectors and measure the resistance from one side of the in-line connector to the matching component harness connector. If the open goes away, the open is on the other side of the in-line connector.
- If this is a fused circuit, make sure to inspect the fuse. If the fuse is open, check the circuit for a short to ground before installing a new fuse. The circuit may have a short to ground causing the fuse to open. This short to ground could be in the wire harness or in one of the components the circuit is supplying voltage to.