Introduction
Troubleshooting the Machine Monitoring System requires additional information from the Service Manual for the particular machine. The Electrical System Schematic and the Operation and Maintenance Manual are required support material.
As a guide, a typical schematic for a Machine Monitoring System is at the end of this manual. For an accurate representation of the Electrical System Schematic for the machine that is being diagnosed, refer to the Service Manual for the machine.
When the troubleshooting procedure instructs you to "REPAIR THE HARNESS", use the Electrical System Schematic in the Service Manual to trace the circuit.
Perform continuity checks at connectors in order to locate harness failures. At component connectors, always check the ground circuit. Less than five ohms of resistance is required between the ground contacts for the connector and frame ground.
Excessive ground resistance that is greater than approximately five ohms can cause an incorrect diagnosis of problems.
During troubleshooting, inspect all component and harness connections before any component is replaced. If these connections are not clean and tight, electrical problems can occur. The problems could be permanent or intermittent. Be sure that the connections are tight before the tests are performed.
Failure of an electrical component can cause the failure of one or more other components. Always try to find the cause and correct the cause of the failure in the electrical system beforeyou replace a component.
| Required Tools | ||
|---|---|---|
| Part Number | Part Description | Qty |
| 6V-7070 | Digital Multimeter or Equivalent | 1 |
| 8T-3224 | Needle Tip Group | 1 |
| 7X-1710 | Multimeter Probe | 1 |
 | |
| Illustration 1 | g00566364 |
Caterpillar Digital Multimeter | |
Use the 6V-7070 Digital Multimeter or an equivalent meter for making continuity checks or voltage measurements. For instruction on the use of the 6V-7070 Digital Multimeter, refer to Special Instruction, SEHS7734. The 7X-1710 Multimeter Probe is used to make measurements at connectors without disconnecting the connectors.
Note: The use of a continuity tester such as the 8T-0500 Continuity Tester or the 5P-7277 Voltage Tester is not recommended on the present Caterpillar electrical circuits. These testers may be used for harness tests when the harness is disconnected from the machine at both ends.