Schematics
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| Illustration 1 | g01072788 |
Schematics are basically line drawings that explain how a system works by using symbols and connecting lines. Symbols are used to represent devices or components of both simple and complex electrical and electronic systems. Schematic symbols are used extensively in Caterpillar publications for diagnosing electrical concerns.
Schematics are used by technicians in order to determine how a system works, and to assist in the repair of a system that has failed.
Schematic symbols present a great deal of information in a small amount of space. The reading of schematic symbols requires highly developed skills and practice. A logical, step by step approach to using schematic diagrams for troubleshooting begins with the technician's understanding of the complete system. Although, there are many electrical symbols that are used in circuit diagrams, Illustration 1 shows the more common Caterpillar electrical symbols.
Schematic Features
Caterpillar electrical schematics contain very valuable information. The information is printed on the front and reverse side of the schematic. The technician needs to become very skilled in reading and interpreting all the information that is contained on both sides of the schematic.
The following features are found on the front of a schematic:
- Color codes for circuit identification
- Color abbreviation codes
- Symbol descriptions
- Wiring harness information
- Schematic notes and conditions
- Grid design for component location
- Component part numbers
The following information is recommended for clearing up the confusion that is associated with dashed lines:
- Dashed colored lines represent attachment circuits. Use the color identification code that is located on the schematic in order to determine the circuit.
- The heavy double dashed lines identify the circuitry and components that are located in the operator station.
- A dashed (thin black) line is used to identify an attachment, wire, cable, or component. (See the symbol description on the schematic).
Machine Electrical Schematics with New Format
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| Illustration 2 | g01072790 |
Some Caterpillar machines use a new format for electrical system schematics. The new format is called PRO/E and provides additional information for wire, connector, component and splice symbols. The following information describes the new format.
Wire Identification Labels
Illustration 2 shows the new wire identification format. The label includes the circuit identification wire label number "169", harness identification code "H", the wire number in the harness "5", color code "PK" and the wire size "18".
Note: The codes that are shown are examples of the new identification system. Consult the appropriate electrical schematic for more detailed, accurate information.
Connectors
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| Illustration 3 | g01072793 |
The new connector identification format includes the harness identification code "H", identifies the assembly as a connector "C", identifies the number of the connector within the harness "7", and lists the connector part number 3E3382.
Note: The codes that are shown are examples of the new identification system. Consult the appropriate electrical schematic for more detailed, accurate information.
Components
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| Illustration 4 | g01072792 |
The previous method of component labeling on a schematic shows the descriptive name and the component part number. The schematics that are drawn in PRO/E format contain a harness identification letter "H", and a serializing code "P-12". "P" stands for part and "12" stands for harness position (number "12" part in harness "H"), and the component part number 113-8490 .
Note: The codes that are shown are examples of the new identification system. Consult the appropriate electrical schematic for more detailed, accurate information.
Splices
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| Illustration 5 | g01072794 |
The PRO/E format for splices uses two connection points to indicate which side a given wire exits. The previous splice symbol used a simple filled in dot to indicate a splice.
The new format shows that in harness "G", wire "405-G9 GY-16" is spliced into two wires, "405-G7 GY-18" and "405-G14 GY-18".
Note: The codes that are shown are examples of the new identification system. Consult the appropriate electrical schematic for more detailed and accurate information.
The following features are listed on the back of the schematic:
- Harness and wire electrical schematic symbols and identification
- Electrical schematic symbols and definitions
- Wire description chart
- Related electrical service manuals
- Harness connector location chart
- Off machine switch specifications
- Machine harness connector and component locations, identified as a machine silhouette
- Component Identifier (CID) list and flash code conversion
- Component location chart
- Resistor and solenoid specifications
- Failure Mode Identifier (FMI) list