HARNESS AS-PUMP 2595344 - Caterpillar

Illustration 1 g02405976
View of the rear of the torque converter (1) Modulating valve (torque converter lockup clutch)
Illustration 2 g02206575
Modulating valve (torque converter lockup clutch)The modulating valve for the torque converter lockup clutch (1) is mounted to the rear of the torque converter housing.The modulating valve is an output of the chassis electronic control module (ECM). The modulating valve for the torque converter lockup clutch is a proportional solenoid valve. The modulating valve is used by the chassis ECM to directly modulate the oil pressure that is sent to the torque converter lockup clutch. When the operator selects a direction, or when the operator selects a speed, the chassis ECM sends a pulse width modulated (PWM) signal in order to vary the current to the clutch solenoid. The distance that is traveled by the solenoid plunger (valve) is proportional to the electrical current of the solenoid. The position of the solenoid plunger (valve) controls the oil pressure of the selected clutch. The amount of current that is sent to the modulating valve regulates the amount of oil pressure that is supplied to the selected clutch. When the chassis ECM sends the maximum current to the modulating valve, the oil pressure in the clutch is at the maximum. When no current is sent to the modulating valve, the oil pressure in the clutch is at the minimum.The modulating valve has a connector with two contacts. One contact receives power from the corresponding connector contact of the chassis ECM. The other contact of all the modulating valves join. The contacts return power to connector contact of the chassis ECM.Note: The solenoid coil is not designed to operate at 24 DCV directly. The chassis ECM sends a 24 V PWM signal at a duty cycle which provides an average voltage of about 12 V to the solenoid coil. Do not energize the solenoid coil with 24 DCV (+battery). The life of the solenoid coil will be drastically reduced if the solenoid coil is energized with 24 DCV (+battery). If the solenoid coil must be energized by a source that is different from the chassis ECM, use 12 DCV to energize the solenoid coil.ReferenceFor information on calibrating the modulating valves, refer to the Service Manual module for Testing and Adjusting, "Calibration and Programming" for the machine that is being serviced.