User's Manual

Test For An Open Circuit
Table 19
Troubleshooting Test Steps
Values Results
1. Identify Open Circuit
A. Identify the connectors and the wire numbers of the sus-
pect circuits. Use the Electrical System Schematic of the ma-
chine to identify the circuits.
B. Turn the key start switch and the disconnect switch OFF.
C. Disconnect the component and the ECM from the wiring
harness.
D. At one of the disconnected harness connections, place a
jumper wire from the contact of the suspect wire to frame
ground.
E. At the other connector of the machine harness, use the
multimeter probes to measure the resistance. Measure the
resistance from the contact of the suspect wire to frame
ground.
The resistance is
less than 5 Ω.
OK - The harness circuit is correct.
STOP
NOT OK - The resistance is greater than 5K Ω. There is
an open in the machine harness.
Repair: Repair or replace the machine harness.
Note: A resistance that is greater than 5 Ω but less than
5K Ω would indicate a loose connection or a corroded con-
nection in the circuit. A resistance measurement that is
greater than 5K Ω would indicate an open in the circuit.
STOP
i06229337
Wiring Harness (Short Circuit)
- Test
SMCS Code: 1408-038
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. A short
across the wires in a circuit for a lamp produces too
much current in the wires but no current 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 Electrical System Schematic for the machine
that is being serviced.
50 UENR7061
Circuit Tests