WD Catalog 2018

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Chapter 4 – Air Conditioner Components
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• All compressor designs function as pumps to move or circulate
refrigerant inside the AC system. Compressors are driven
through a clutch pulley and V-belt by the engine. For efficient
operation, a compressor must be mounted securely with proper
belt tension and alignment. Engine speed and suction pressure
have an effect on compressor output. Higher engine RPM means
greater output.
• The clutch is used to drive the compressor. In most AC systems a
thermostat cycles the clutch on and off, although in some designs
the clutch stays on during AC operation.
• Condenser construction allows heat energy transfer to the outside
air. Refrigerant changes state in the condenser, from a high pres-
sure and temperature gas to a liquid. It is important to keep the
condenser free of dirt and debris for good air flow through the fins
and efficient heat transfer. The various condenser designs all
function the same way.
• Receiver-driers function as a refrigerant drier, filter and tempo-
rary storage tank. The filter and desiccant material trap and hold
moisture or other contaminants that may be inside the AC sys-
tem. The receiver-drier traps any vapor leaving the condenser.
Some designs incorporate a sight glass, moisture indicator and/or
various other control devices.
• An accumulator may be used in place of the receiver-drier as a
temporary storage tank for refrigerant. This device controls the
flow of refrigerant to the compressor and also traps contaminants
and moisture. Accumulators are used with AC system designs
that have an expansion tube. They prevent liquid refrigerant from
flowing to the compressor.
• There are a variety of thermostatic expansion valves (TXV’s) and
other refrigerant flow regulating devices in use today. All control
the flow of refrigerant in the AC system to manage the movement
of heat energy. There is the block expansion valve, traditional
expansion valve, and expansion tube. Some AC system refriger-
ant flow regulating assemblies combine several components to
control refrigerant flow.
• The construction of an evaporator coil is designed to transfer heat
energy from the cab air to the refrigerant inside the tube. The
evaporator coil also helps to clean and dehumidify the air in the
cab. Moisture in the air condenses on the fins of the evaporator
coil, then drips off the fins and drains out of the cab. When
refrigerant enters the evaporator there is a quick drop in pres-
sure. The refrigerant expands rapidly, changes state and drops in
temperature.
• Blower, fan and motor assemblies increase the movement of air
for efficient cooling (heat energy transfer). The duct system con-
trols the air flow direction.
• The hoses and fittings used in AC systems connect the various
components together. They enclose or contain the refrigerant as it
moves around inside the system.