For proportional solenoids, the ECM uses a pulse width modulated (PWM) signal in order to vary the current to the solenoid. The distance the solenoid plunger valve travels is in proportion to the electrical current sent by the ECM.
For on/off solenoids, the ECM uses a +V signal in order to turn the solenoid on and a ground signal to turn the solenoid off. The plunger valve has only two positions.
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| Illustration 1 | g01107070 |
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Left forward EDC solenoid, left reverse EDC solenoid, right forward EDC solenoid, right reverse EDC solenoid | |
The function of these PROPORTIONAL solenoids is to control the output flow from each propel pump. This flow determines the speed and direction of each of the propel motors. The ECM varies the current to the solenoids depending the selected speed and direction that is set by the operator using the speed dial, lever, brake pedal, and steering wheel. The current to these solenoids controls the valve position. Typical operating range for this solenoid is 0 to 100 milliamps as pump output varies from zero to maximum flow. Solenoid coil resistance is about 27 ohms.
High Gear Solenoid, Travel Solenoid
The function of this ON/OFF solenoid is to change the gear ratio of the propel motors. When this solenoid is energized, the motor is switched to a lower planetary ratio. This solenoid is directly controlled by an "ON" (24 DCV) or "OFF" (0 DCV) voltage from the ECM. Solenoid coil resistance is about 27 ohms.
Parking Brake Solenoid, Pave Solenoid
The purpose of the parking brake valve is to engage the parking brake. The brake is spring applied and hydraulically released. When the operator places the speed lever in the NEUTRAL position, the ECM de-energizes the parking brake solenoid in order to relieve the hydraulic pressure for the brake. This causes the parking brake to engage. When the machine is not in NEUTRAL, the brake pedal is not fully depressed, and there are no diagnostic codes which require resets, the ECM will energize the solenoid. This directs hydraulic pressure to the brake and the parking brakes is disengaged. The ECM uses a +V signal to activate the parking brake solenoid.