HARNESS AS-HEATER & AIR COND 2397415 - Caterpillar

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Solenoid valve (transmission clutch)The solenoid valves are outputs of the Power Train Electronic Control Module (ECM). The purpose of the solenoid valve is to direct pilot oil to the ends of the control spool. The control spool will move. This allows pressure oil to flow to the corresponding clutches. The Power Train ECM energizes the appropriate solenoid valve for the required clutches for the speed and for the direction that has been selected.Solenoids (4) and (5) are for direction. Solenoids (1), (2), (3) and (6) are for speed.In order for the machine to move, one speed solenoid and one direction solenoid must be energized. When the transmission is in neutral, solenoid valve (1) is energized. When the transmission is in neutral, solenoid valves (2), (3), (4), (5) and (6) are de-energized.The solenoid valves have a connector with two contacts. Connector contact 1 receives power from the corresponding connector contact of the Power Train ECM (J1-48, J1-49, J1-51, J1-62, J1-65 and J1-66). Connector contact 2 of all the solenoid valves join together. These wires return power to connector contacts J1-50, J1-55 and J1-60 of the Power Train ECM.
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Pulse and hold chartThe solenoid valves use a pulse and hold strategy to extend the life of the coil of the solenoid valves. The Power Train ECM has the capability of controlling the amount of current from the output. For ON/OFF type solenoids, the current needed to engage a solenoid is higher than the current needed to hold the solenoid engaged. The pulse and hold strategy makes use of this characteristic of a solenoid by setting the current to the solenoid to maximum and then reducing the current to a lower level after one second. Lowering the current to the valve reduces the heat that is dissipated by the coil of the solenoid.Note: The solenoid coils are not designed for direct 24 DCV operation. The Power Train ECM sends a 24 volt PWM signal at a duty cycle which provides an average voltage of about 8 to 12 volts to the solenoid coils. Do NOT activate the coils with 24 DCV (+battery) or the life of the coils will be drastically reduced. If the coils must be activated by means other than the ECM, use a 12 DCV source.Note: The Power Train ECM momentarily prevents the energizing of solenoid valve (1), as the operator shifts from forward direction to reverse direction or shifts from reverse direction to forward direction. Energizing of the solenoid is delayed for two seconds when the operator selects neutral. During this delay, the transmission is in a "no clutch neutral" state. All of the solenoid valves are de-energized during the "no clutch neutral" state. This "no clutch neutral" state is provided in order to improve the quality of directional shifts.ReferenceFor information on the transmission hydraulic control system, refer to Systems Operation, "Transmission Hydraulic Control".ReferenceFor information on diagnostic operations refer to Systems Operation, "Power Train Electronic Control System".ReferenceFor information on the Power Train ECM, refer to Systems