Case 580SR, Service Manual

Page: 780 / 1068

20 SECTION 50 - CAB HEATING AND AIR CONDITIONING
COMPRESSOR
The air conditioning compressor is mounted on the
left hand side of the engine and is belt driven from
the crankshaft pulley.
The compressor separates the low and high pres-
sure sides of the system and has two functions:
1. To raise the refrigerant temperature by com-
pression to a higher degree of temperature than
the ambient (outside air) temperature.
2. To circulate the required volume of refrigerant
through the system.
The refrigerant compressor is a seven cylinder wob-
ble plate unit housed in a die cast aluminium hous-
ing.
Drive to the wobble plate is from the pulley, through
the electro-magnetic clutch to the main driveshaft.
Attached to the driveshaft is a cam rotor which oscil-
lates the wobble plate. The wobble plate is prevent-
ed from rotating by a static gear engaging with teeth
formed in the face of the plate. The seven pistons are
connected to the wobble plate by rods located in ball
sockets.
Refrigerant is drawn in on the downward stroke of a
piston through the reed valves located either end of
the cylinder assembly. Refrigerant enters the cylin-
der assembly through a gallery in the outer circum-
ference of the cylinder assembly.
During the upward stroke, the piston compresses the
refrigerant and expels it through another reed valve
into an inner gallery in the cylinder and, from here,
out into the coolant system.
The compressor is lubricated with a Polyalklene Gly-
col (PAG) oil Type SP20. This oil can be mixed with
coolant and is carried around in the coolant system
itself.
The compressor is activated by an electro-magnetic
clutch which functions to engage or disengage the
compressor as required in the operation of the air
conditioning system.
The clutch is primarily activated by the:
Z
temperature control
Z
low pressure cut-out switch
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