Komatsu 830E, Shop Manual

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M9-4 Air Conditioning System 05/02 M09010
for HFC 134a Refrigerant
AIR CONDITIONER SYSTEM
COMPONENTS
COMPRESSOR (Refrigerant Pump)
The compressor is where the low pressure side of the
system changes to high pressure. It concentrates the
refrigerant returning from the evaporator (low side) cre-
ating high pressure and a temperature much higher
than the outside air temperature. The high temperature
differential between the refrigerant and the outside air
is necessary to aid rapid heat flow in the condenser
from the hot refrigerant gas to much cooler outside air.
To create high pressure concentration, the compressor
draws in refrigerant from the evaporator through the
suction valve and during compression strokes, forces it
out through the discharge valve to the condenser. The
pressure from the compressor action moves the refrig-
erant through the condenser, receiver-drier and con-
necting hoses to the expansion valve.
The compressor is driven by the engine through a v-
belt driving an electrically operated clutch mounted on
the compressor drive shaft.
SERVICE VALVES
Quick-connect hose end fittings with integral service
valves attach to system service ports for servicing the
unit. A manifold gauge set is connected into the system
at the service valve ports and all procedures, such as
discharging, evacuating and charging the system, are
performed through the service valves.
CONDENSER
The condenser receives the high pressure, high-tem-
perature refrigerant vapor from the compressor and
condenses it to high pressure, hot liquid.
It is designed to allow heat movement from the hot
refrigerant vapor to the cooler outside air. The cooling
of the refrigerant changes the vapor to liquid. Heat
exchange is accomplished using cooler air flowing
through the condenser. Condenser cooling is achieved
by air flowing from the radiator fan along with ram air
provided by vehicle movement. The radiator fan moves
more than 50% of condenser air flow unless travel
speed is at least 25 mph.
Ram air condensers depend upon the vehicle move-
ment to force a large volume of air past the fins and
tubes of the condenser. The condenser is usually
located in front of the radiator or on the roof of the
truck.
Condensing of the refrigerant is the change of state of
the refrigerant from a vapor to a liquid. The action is
affected by the pressure of the refrigerant in the coil
and air flow through the condenser. Condensing pres-
sure in an AC system is the controlled pressure of the
refrigerant which affects the temperature at which it
condenses to liquid, giving off large quantities of heat
in the process. The condensing point is sufficiently high
to create a wide temperature differential between the
hot refrigerant vapor and the air passing over the con-
denser fins and tubes. This difference permits rapid
heat transfer from the refrigerant to ambient air.
RECEIVER-DRIER
The receiver-drier is an important part of the air condi-
tioning system. The drier receives the liquid refrigerant
from the condenser and removes any moisture and for-
eign matter present which may have entered the sys-
tem. The receiver section of the tank is designed to
store extra refrigerant until it is needed by the evapora-
tor. The storage of this refrigerant is temporary and is
dependent on the demand of the expansion valve.
A desiccant is a solid substance capable of removing
moisture from gas, liquid or solid. It is held in place
within the receiver between two screens, which also
act as strainers.
The receiver-drier is also equipped with a sight glass
and a moisture indicator. The sight glass can give a
good indication of the charge of the system. If the sight
glass is not clear, the system is low on refrigerant.
The moisture indicator is a device to notify service per-
sonnel that the drier is full of moisture and must be
replaced. The indicator is blue when the component is
free from moisture. When the indicator turns beige or
tan, the drier must be replaced.