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| Illustration 1 | g01362475 |
Parking brake circuit | |
The components of the parking brake circuit are the parking brake switch, the transmission oil pressure sensor, the brake accumulator oil pressure switch for brake application, the brake accumulator oil pressure switch for alert indicator, the parking brake solenoid 1, the parking brake solenoid 2, the parking brake oil pressure switch and the Power Train/Chassis Electronic Control Module (Power Train/Chassis ECM).
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| Illustration 2 | g01418203 |
(1) Parking brake switch | |
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| Illustration 3 | g01411270 |
(2) Transmission oil pressure sensor | |
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| Illustration 4 | g01411272 |
(3) Brake accumulator oil pressure switch for alert indicator (4) Brake accumulator oil pressure switch for brake application | |
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| Illustration 5 | g01411281 |
(5) Parking brake solenoid 1 (6) Parking brake solenoid 2 (7) Parking brake oil pressure switch | |
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| Illustration 6 | g01434326 |
Front view of cab (front cover removed) (8) Power Train/Chassis ECM | |
With the battery disconnect switch in the ON position, 24 volt power is supplied from the batteries via circuit breaker 1 to Power Train/Chassis ECM (8) .
With the key start switch in the ON position, 24 volt power is supplied from the batteries via circuit breaker 13 to transmission oil pressure sensor (2) and Power Train/Chassis ECM (8).
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| Illustration 7 | g01418204 |
(9) Caterpillar Monitoring System (10) Parking brake alert indicator (11) Transmission fault indicator | |
When parking brake switch (1) is moved to the ON position, 24 volt power from Power Train/Chassis ECM (8) to parking brake solenoid 1 (5) and parking brake solenoid 2 (7) is interrupted. The pressure oil in the wheel brakes is returned to the hydraulic tank and the parking brake is engaged. In this condition, parking brake oil pressure switch (6) sends a signal to Power Train/Chassis ECM (8). Power Train/Chassis ECM (8) sends a signal via the CAT Data Link to Caterpillar Monitoring System (9). Caterpillar Monitoring System (9) turns on parking brake alert indicator (10) .
When the key start switch is in the ON position and parking brake switch (1) is in the OFF position, parking brake switch (1) must be cycled to allow the parking brake to disengage.
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| Illustration 8 | g01418205 |
(12) Brake accumulator oil pressure alert indicator | |
If the oil pressure in the service brake system decreases below a preset value, contacts in brake accumulator oil pressure switch for alert indicator (3) will close, this will cause brake accumulator oil pressure alert indicator (12) to turn on. If the oil pressure decreases further, contacts in brake accumulator oil pressure switch for brake application (4) will close. This will cause Power Train/Chassis ECM (8) to de-energize parking brake solenoid 1 (5) and parking brake solenoid 2 (7). The parking brake will be engaged.
If the oil pressure in the transmission decreases below a preset value, this change is sensed by transmission oil pressure sensor (2). A signal is sent to Power Train/Chassis ECM (8). Power Train/Chassis ECM (8) sends the signal to Caterpillar Monitoring System ECM (9) to illuminate transmission fault indicator (11). If the transmission oil pressure decreases further Power Train/Chassis ECM (8) will de-energize parking brake solenoid 1 (5) and parking brake solenoid 2 (7). The parking brake will be engaged.
If parking brake switch (1) is moved to the OFF position, power from Power Train/Chassis ECM (8) is supplied to energize parking brake solenoid 1 (5) and parking brake solenoid 2 (7). This will allow pressure oil to flow to the wheel brakes to disengage the parking brakes. Parking brake alert indicator (10) will turn off.