The change of the revolution speed of the blower at different speeds depends on the blower motor control module
controlled by the blower motor revolution speed control device. If the user selects the maximum A/C mode, the
vast majority of the air entering the blower is from the passenger compartment (inside circulation).
Outside air enters into the vehicle in the following mode under most of operational conditions:
–
Blower motor word breathe the outside atmosphere
–
Vehicle forward running was pressed into outside air
The blower motor blows air along the following line:
–
Pass through evaporator core
–
Pass through heating core
–
Enter into the passenger compartment
B. Heater
core
The heater core is the main part of the heater system. The heater core is located in the A/C head unit. When the
engine is running, the engine coolant is pumped from the engine to the heater core, the heat fro the engine coolant
is transmitted by the heater core to the air flowing through the heater core. The heater core is provided with
special inlet and outlet warm air water pipe. The HVAC water pipeline of the heater core body must be thoroughly
drained during dismantled. During maintenance, the heater core with the independent warm air water pipeline
must have been installed. The heater core is equipped with the temperature sensor; the sensor transmits the surface
temperature signal of the heater core to the A/C control module for providing more compensation parameters to
the automatic A/C.
C. Evaporator
and expansion valve
The evaporator is located at the left of the A/C head unit. When installed on the vehicle, the A/C head unit needs
to be dismantled to dismantle and install the evaporator and the expansion valve. The refrigerant pipeline of the
evaporator must be thoroughly drained during dismantlement. During maintenance, the evaporator with the
independent refrigerant pipeline must have been installed. The expansion valve is connected with the evaporator,
installed at one end of the evaporator and located at the inlet of the evaporator; one side of the expansion valve is
connected with the air inlet pipe and the exhaust pipe of the A/C compressor and the other side thereof is
connected with the air inlet pipe and the exhaust pipe of the evaporator; the high-pressure liquid refrigerant is
limited in the liquid pipeline so that the refrigerant becomes the low-pressure liquid when flowing to the
evaporator.
Expansion valve changes the position from large to small according to the lower limit of the A/C pressure and the
upper limit of the A/C pressure.
The evaporator is cooled and dehumidified before the air enters the passenger compartment. The following
processes are generated in the evaporator:
–
Low pressure temperature fluid /vapor refrigerant enter into evaporator.
–
Refrigerant flows through evaporation pipe.
– Refrigerant
vaporizes.
–
Absorb heat, when refrigerant vaporises, air flow absorb heat by evaporator
– Refrigerant enters into evaporator in the form of low pressure and low temperature, and leaves from
evaporator in the form of steam.
When the heat in air is transmitted to the evaporator core, moisture in air will be condensed on the outer surface of
the evaporator core to for water to flow outside.
The evaporator is equipped with a temperature sensor to prevent from freezing. The sensor measures the surface
temperature of the radiating fin on the evaporator, the compressor clutch will not continue to work if the
temperature is lower than about 2℃ (36 ºF). If the temperature is increased to above 4℃ (39 ºF), the compressor
will start working again. In the system with automatic temperature control, the sensor signal is firstly transmitted
to the A/C module, and then is transmitted to the A/C pressure switch through a special line; if the A/C pressure
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