WEIGHT-ADVANCE 8N8997 - Caterpillar

Inputs
The inputs describe the status of the machine systems. Two types of inputs exist. The inputs can be either a Switch type or a sensor type. Switches provide an open, a ground, or a + battery signal to the inputs of the controller. Sensors (frequency, PWM, or voltage) provide a changing signal to the sensor inputs of the controller. The inputs to ECMs are listed in table .Sensors
Illustration 2 g03399469Cab Air and Cab Ventilation Duct Air Temperature Sensors
Cab Air and Cab Ventilation Duct Air Temperature Sensors are PWM inputs to the Implement ECM. These two sensors are used to determine average cab air temperature.Operator Controls
Illustration 3 g03399472
(A) A/C mode
(B) Off mode
(C) Automatic temperature control mode
(D) Temperature dial
(E) Blower speed dial HVAC Blower Speed Control Position
The fan control position, controls the speed of the HVAC blower motor. Full counter clockwise position is the off position and the full clockwise position is the maximum fan speed. The dial is a potentiometer that provides an infinite variable blower speed option allowing the operator to choose the correct airflow quantity.Note: Do not turn the blower speed dial to the full counter clockwise position unless you want to shut off the HVAC system.High/Low Pressure Switch
Illustration 4 g03399567
High-pressure switch
Illustration 5 g03399568
Low-pressure switch
High/Low pressure switch, used to prevent unwanted high pressure and low-pressure conditions on the outlet of the A/C compressor. Low-pressure switch, used to prevent unwanted low-pressure conditions on the inlet side of the A/C compressor. Both the high/low and low-pressure sensors prevent operation of the A/C compressor during conditions of overcharge of the refrigerant and undercharge of the refrigerant.HVAC Evaporator Thermostat Switch
Illustration 6 g03399572The HVAC evaporator thermostat switch is a passive analog signal to the Implement ECM. This sensor is used to measure the temperature of the evaporator coil. The sensors operating range is MAX 120° C (248° F), MIN −40° C (−40° F).Outputs
Clutches
HVAC A/C Clutch
Illustration 7 g03399574
Illustration 8 g03399576
(3) Magnetic clutch and pulley assembly
(4) Coil assembly
(5) Drive plate
(6) Bearing
(7) Compressor shaft The Implement ECM energizes the air conditioning clutch when the operator requests air conditioning and all of the conditions have been met.The compressor is driven by the engine. A belt connects the engine to the clutch and pulley assembly (3). The pulley assembly is located on the clutch. The drive plate (5) is fastened to the shaft of the compressor. The clutch and pulley assembly (3) turns on the bearing (6). The clutch and pulley assembly (3) are not connected to the shaft (7). The electric current from the thermostat controls a magnetic field in the coil assembly (4).The magnetic field pulls the drive plate (5) against the clutch and pulley assembly (3). The clutch and the pulley assembly (3) turns the shaft (7) that operates the compressor. When the current to the coil assembly (4) is stopped, the magnetic field is removed. This action allows the drive plate (5) to move away from the clutch and pulley assembly (3). The clutch and the pulley assembly (3) will turn freely on the bearing (6). The sequence of connecting