Colored Electrical Schematic
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| Illustration 1 | g01229718 |
Propel Control Circuit | |
Note: The electrical system on this machine is wired according to the Caterpillar corporate wiring system. In Caterpillar corporate wiring, each wire has a color and a number. Each color and each number has a specific meaning.
The meaning for the following colors are:
- Red wires are positive.
- Back wires are negative.
- Orange wires are in starting circuits.
The meaning for the following numbers are:
- 100 wires are power circuits.
- 200 wires are ground.
- 300 wires are machine basic circuits
- 400 wires are monitoring circuits.
- 500 wires are accessory circuits.
- 600 wires are lighting circuits.
- 700 to 999 wires are control circuits.
Power Distribution
When the electrical disconnect switch is in the ON position, power is available at the engine ECM circuit breaker and power is available at the main circuit breaker. The engine ECM circuit breaker transfers power to terminal "J1-48" and to terminal "J1-52" of the engine ECM. The engine ECM is grounded at terminal "J1-61" and at terminal "J1-63".
The main circuit breaker transfers power to the main power relay.
When the main power relay is energized, power is available at the following circuit breakers:
- "CB1"
- "CB2"
- "CB11"
The 103-YL wire transfers power from circuit breaker "CB1" to contact "1" of the left parking brake switch. The 103-YL wire also transfers power to contact "2" of the shift switch. The 119-PK wire transfers power from circuit breaker "CB2" to the "A" contact of the propel lever sensor. The 119-PK wire also transfers power to terminal "1" of the machine ECM. The 199-OR wire transfers power to contact "2" of the flow divider switch.
Parking Brake Switch
The machine ECM monitors the circuits across the parking brake switches at terminal "12" and at terminal "25". When the circuit at terminal "12" is complete and the circuit at terminal "25" is open, the machine ECM determines that both parking brake switches are in the ON position. When the circuit at terminal "12" is complete and the circuit at terminal "25" is open, the machine ECM determines that at least one parking brake switch is in the ON position. When the circuit at terminal "12" is open and the circuit a terminal 25 is complete, the machine ECM determines that both of the parking brake switches are in the OFF. When the circuit at terminal "12" and the circuit at terminal "25" are both complete or both open, the machine ECM logs a fault. In this case, the machine ECM engages the parking brake. When the parking brake is engaged, the machine ECM disables machine propulsion.
Parking Brake Solenoid
The parking brake switch also controls the parking brake solenoid. When both parking brake switches are in the OFF position, power transfers into the L939-GN wire and to the parking brake solenoid. When the parking brake solenoid is energized, the parking brakes are released.
Propel Lever Sensor
The propel lever sensor sends a pulse width modulated signal from contact "C" to terminal "27" of the machine ECM. The duty cycle of the signal varies between five percent and 95 percent. The frequency of the signal is 5000 Hz. The duty cycle increases as the propel lever is moved out of the NEUTRAL position. The duty cycle is proportional to the position of the propel lever.
Parking Brake Switch ON to OFF (Propel Lever in the NEUTRAL Position.
If the machine ECM determines that the propel lever is out of the NEUTRAL position when the parking brake switch is moved from the OFF position to the ON position, the machine ECM will not allow the machine to move. In this case, the propel lever must be returned to the NEUTRAL position before the machine ECM will again use the input from the propel lever sensor in order to move the machine.
Travel Direction and Travel Speed Control
The machine ECM monitors the condition of the circuit at terminal "14" and the condition of the circuit at terminal "15" in order to determine the desired travel direction. The L924-PK wire connects terminal "14" of the machine ECM to contact "1" of the travel direction switch which is on the right side of the instrument panel. The L925-PU wire connects terminal "15" of the machine ECM to contact "6" of the travel direction switch which is on the right side of the instrument panel.
The travel direction switches are wired in a series circuit. When both travel direction switches are in the HOLD position, the circuit at terminal "14" and the circuit at terminal "15" of the machine ECM are complete. When one of the travel direction switches is in the FORWARD position, the circuit at terminal "14" is complete, and the circuit at terminal "15" is open. When one of the travel direction switches is in the REVERSE position, the circuit at terminal 14 is open, and the circuit at terminal "15" is closed.
After the machine is started, the travel direction logic in the machine ECM defaults to hold. The machine ECM will not allow the machine to move, regardless of the position of the propel lever. If the parking brake switch is in the ON position, the machine ECM resets the travel direction logic to hold.
When one of the travel direction switches is moved into the FORWARD position, the machine ECM detects a closed circuit at terminal "14" and an open circuit at terminal "15". This situation tells the machine ECM in order to initiate forward propel logic. When the operator releases the travel direction switch, the switch returns to the HOLD position. The circuit at terminal "14" and the circuit at terminal "15" are now both closed. However, the machine ECM continues to operate following the forward propel logic until the operator moves a travel direction switch to the REVERSE position, or until the operator moves the parking brake switch to the OFF position.
When the machine ECM determines that the operational parameters for forward travel have been met, the machine ECM monitors the duty cycle of the propel lever sensor in order to determine the output signal which is to be sent to the forward EDC. This output signal is generated at terminal "11". The output signal is pulse width modulated. The duty cycle of the output signal is proportional to the duty cycle of the signal from the propel lever sensor.
Load Control
While the machine is traveling and the rotor is operating, the machine ECM monitors the input from the engine ECM in order to control the load on the engine. When the machine encounters a load which causes the engine speed to fall to 2050 rpm, the machine ECM decreases the signal which is sent to the forward EDC. This causes the machine to slow and causes the engine speed to remain at a minimum of approximately 2050 rpm. As the load on the machine decreases and the engine speed increases above 2050 rpm, the machine ECM gradually increases the signal which is sent to the forward EDC. Eventually, the signal to the EDC matches the propel lever setting.
Motor Shift Control
When the shift switch is in the "L" position, contact "2" and contact "3" are open. In this case, the shift solenoid is de-energized. When the shift switch is in the "H" position, contact "2" and contact "3" of the switch are closed. In this case, the C742-OR wire transfers power to the shift solenoid.
Flow Divider Control
When the flow divider switch is in the OFF position, contact "1" and contact "2" are open. In this case, the flow divider solenoid is de-energized. When the flow divider switch is in the ON position, contact "1" and contact "2" are closed. In this case, the 556-WH wire transfers power to the flow divider solenoid.