Komatsu Galeo PC138US-8 Shop Manual page 252

SEN02552-01
Functions of major components
Evaporator
Evaporator fin is cooled by the low-pressure,
q
low-temperature refrigerant gas being sent
from the expansion valve. Air from the blower
motor is cooled and dehumidified when pass-
ing through the fin.
Heater core
Fin of the heater core is heated by the hot
q
water (coolant) being sent from the engine. Air
from the blower motor is heated as it passes
through the fin.
Expansion valve
This valve converts high-pressure, high-tem-
q
perature liquid refrigerant from the condenser
to low-pressure, low-temperature misty refrig-
erant through the throttling function.
It controls flow rate of refrigerant by changing
level of throttling depending on the thermal
load in the operator's cab.
Blower motor
It suctions air by rotating the fin installed on the
q
blower motor. And it is also used for sending
air to the evaporator and heater core.
Air mix damper actuator
It starts the built-in motor upon receipt of a sig-
q
nal current from the air conditioner controller in
order to open or close the air mix damper
through the link mechanism.
The motor rotating direction is determined as
q
the air conditioner controller reads the position
of the potentiometer being built in the actuator.
This reading is done as the target temperature
is set on the machine monitor.
Rotation of the motor is stopped as the con-
q
tact, which is to move interlocked with the
motor, or when signal current from the air con-
ditioner controller is turned "OFF".
Mode selector damper actuator
It starts the built-in motor upon receipt of a sig-
q
nal current from the air conditioner controller in
order to open or close the mode selector
damper through the link mechanism.
The motor rotating direction is determined as
q
the air conditioner controller reads the position
of the potentiometer being built in the actuator.
This reading is done as the mode is selected
on the machine monitor.
Rotation of the motor is stopped as the con-
q
tact, which is to move interlocked with the
motor, or when signal current from the air con-
ditioner controller is turned "OFF".
8
10 Structure, function and maintenance standard
Internal/external air changeover damper actua-
tor
It starts the built-in motor upon receipt of a sig-
q
nal current from the air conditioner controller in
order to open or close the internal/external air
flow selector damper through the link mecha-
nism.
The motor rotating direction is determined by
q
selecting internal/external air flow on the
machine monitor.
Rotation of the motor is stopped as the con-
q
tact, which is to move interlocked with the
motor, or when signal current from the air con-
ditioner controller is turned "OFF".
Evaporator temperature sensor
In order to prevent freezing of the evaporator, it
q
senses the evaporator temperature and sends
necessary signals to the air conditioner con-
troller.The signal sent to the air conditioner
controller is used to control the compressor. As
the result, temperature of the air blown out of
the grill is adjusted depending on the volume of
refrigerant circulated in the evaporator.
Internal air temperature sensor
It senses the internal air temperature and
q
sends necessary signals to the air conditioner
controller.The signal sent to the air conditioner
controller is used to control the compressor. As
the result, temperature of the air blown out of
the grill is adjusted depending on the volume of
refrigerant circulated in the evaporator.
PC138US, USLC-8