Case 580SR Service Manual page 781

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SECTION 50 - CAB HEATING AND AIR CONDITIONING 21
Temperature control
The air conditioner temperature control switch is
mounted on the blower motor assembly.
The switch is a device which turns the compressor
clutch on and off to maintain a constant average
evaporator temperature and senses the evaporator
temperature using a thermistor (1).
The temperature control switch compares the volt-
age of the thermistor, which is dependent on the
temperature of the evaporator, with the voltage
across the potentiometer of the "in cab" temperature
control switch.
The switch upon comparing the two voltages deter-
mines whether the compressor clutch should be
switched "on" or "off" in order to maintain the desired
in cab temperature control.
Low pressure cut-out switch
The low pressure switch (1) is mounted in the top of
the filter (2) mounted in front of the radiator behind
the battery.
The purpose of the switch is to shut off the compres-
sor pump in the event of low pressure in the refriger-
ant system.
Low refrigerant pressure may occur due to a faulty
expansion valve, icing up of the expansion valve or-
ifice or refrigerant loss. Low refrigerant pressure
may result in damage to the compressor pump.
The low pressure switch is factory set and cannot be
adjusted.