Product Link - PL102C Caterpillar

A short circuit is a failure of an electrical circuit that results in undesired electrical current. Usually, a short circuit is a bypass of the circuit across a load. For example, a short across the wires in a circuit for a lamp produces too much current in the wires but no current is felt at the lamp. The lamp is shorted out. The resistance in a normal circuit can vary, but the resistance between a particular circuit and other unrelated circuits is always greater than 5000 ohms. The following procedure explains the test for a short circuit.

Reference: For a complete electrical schematic, refer to the Electrical System Schematic for the machine that is being serviced.

TEST FOR A SHORT CIRCUIT.

1. Identify the connectors and the wire numbers of the suspect circuits. Use the Electrical System Schematic of the machine to identify the circuits.

2. Turn the key start switch and the disconnect switch to the OFF position.

3. Unplug the connectors from the PL102C module. Disconnect the suspect wire of the wiring harness from the machine harness.

4. At one of the disconnected PL102C wire harness connections, place a jumper wire from the contact of the suspect wire to frame ground.

5. At the connector of the PL102C, use the multimeter probes to measure the resistance from the contact of the suspect wire to frame ground.

   Expected Result: The resistance is greater than 5000 ohms for all the measurements.

   OK - The resistance is greater than 5000 ohms for all the measurements. The harness circuits are correct.

   Stop.

   NOT OK - The resistance is less than 5 ohms. There is a short in the machine harness. The short is between the suspected wire and the wire with the lowest resistance measurement.

   Repair: Repair the PL102C harness or replace the PL102C harness.

   Stop.