Schematic Diagram of Coolant Lines
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| Illustration 1 | g00376476 |
(19) Heater unit (20) Heater core (25) Coolant return line (26) Coolant supply line (32) Water valve (E) Engine (F) Inside cab | |
The heating system uses coolant from the engine cooling system. Water valve (32) is connected to the control panel in the cab. With the ON/OFF switch in the OFF position, the water valve prevents the flow of coolant through heater core (20). Water valve (32) is actuated when the selected temperature requires heating in order to be attained. The selected temperature is relative to the sensed temperature in the cab. When the water valve opens, warm coolant flows from the engine (E) to the heater core (20). The temperature of the flow of air across the heater core is warmed as the temperature of the heater core increases.
The amount of increase in air temperature is controlled by the amount of coolant that flows through the heater core (20). As the amount of coolant flow increases, the temperature of the air that flows across the heater core increases. The coolant then flows from the heater core back through the engine cooling system.
Operation of Electronics (Manually Controlled System)
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| Illustration 2 | g00291559 |
(1) Fan speed knob (2) OFF position for fan speed (3) Low fan speed (4) Medium fan speed (5) High fan speed (Defroster) (6) Temperature control knob | |
Temperature control knob (6) controls the potentiometer, the electronic control module and the electronic water valve.
When the operator turns temperature control knob (6) to the desired position, the potentiometer sends a modified voltage signal to the electronic control module. The control module applies voltage to the actuator for the water valve in order to change the valve position. Once the predetermined voltage of the potentiometer (feedback) is received at the control module, voltage is removed from the actuator for the water valve. The result is the correct valve position which directly relates to the desired temperature in the cab.
Fan speed knob (1) controls the switches for low fan speed, medium fan speed, and high fan speed. Fan speed knob (1) also controls the blower motor, the protective thermal fuse and the resistor which varies the voltage that is supplied to the blower motor.
When the operator turns the fan speed knob (1) to the desired fan speed, the corresponding voltage is applied to the resistor. The reduced output voltage from the resistor then passes through the protective thermal fuse. Voltage continues from the thermal fuse in order to run the blower motor.