Wiring Harness (Open Circuit) - Test
An open is a failure of an electrical circuit that results in no flow of electrical current. An open circuit is usually caused by failed electrical wires or a poor connection of electrical connectors. If an electrical wire or a connection is broken, then the flow of electrical current through the circuit is interrupted. A normally closed circuit will have less than 5 ohms of resistance. The following procedure explains the test for an open circuit:
Reference: For a complete electrical schematic, refer to Electrical System Schematic for the genset that is being serviced.
TEST FOR AN OPEN CIRCUIT.
- Identify the connectors and the wire numbers of the suspect circuits. Use the Electrical System Schematic of the genset to identify the circuits.
- Turn the disconnect switch to the OFF position.
- Disconnect the components and the ECM from the wiring harness.
- At one of the disconnected harness connections, place a jumper wire from the contact of the suspect wire to frame ground.
- At the other connector of the genset harness, use the multimeter probes to measure the resistance from the contact of the suspect wire to frame ground.
Expected Result: The resistance is less than 5 ohms.
OK - The resistance is less than 5 ohms. The harness circuit is correct.
Stop.
NOT OK - The resistance is greater than 5000 ohms. There is an open in the genset harness.
Repair: Repair the genset harness or replace the genset harness.
Stop.
Caterpillar Information System:
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