214603 310 Revision A
5.7.5 Air Conditioning (A/C) Compressor
The compressor is protected from excessively low suction and high discharge pressures by two switches that shut
down the compressor to prevent damage to the system. These switches do not require regular maintenance.
Contact your MacDon Dealer if you suspect a problem with the switches.
The low pressure switch
The low pressure switch is closed when there is sufficient refrigerant in the system and the pressure is above
234 kPa (34 psi). The system remains pressurized at about 414–483 kPa (60–70 psi) with the compressor off.
When the A/C system is turned on, the compressor starts because the system pressure is above 234 kPa (34 psi).
As the system gets colder, the suction pressure (low side) drops. At 24–86 kPa (3.5–12.5 psi) (for 2014 and prior:
14–55 kPa [2–8 psi]), the switch opens and shuts down the compressor.
When the pressure rises above 172 kPa (25 psi), the switch closes and the compressor restarts. The low pressure
switch is located at the outlet of the evaporator (under cab in the A/C box).
The high pressure switch
The high pressure switch is closed when there is sufficient refrigerant in the system. The system remains
pressurized at about 414–483 kPa (60–70 psi) with the compressor off.
If the pressure exceeds 2482–2620 kPa (360–380 psi) during operation, the valve opens. It will close when
pressure falls below 1517–1931 kPa (220–280 psi). The high pressure switch is located on the receiver drier (right
cab-forward frame rail, behind the fuse panel).
If the compressor cycles rapidly due to rapid pressure changes, the cab display module (CDM) displays a warning
CHECK A/C SYSTEM. Contact your Dealer.
Servicing the Air Conditioning Compressor
Refer to Replacing Air Conditioner (A/C) Compressor Belt, page 347 for belt replacement procedure.
See your MacDon Dealer for all other servicing procedures.
MAINTENANCE AND SERVICING
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