The air conditioning controls the temperature of the vehicle interior. It functions as a dehumidifier, in addition to its heating and cooling temperature control functions. The A/C also helps to remove obstructions such as frost, ice, and condensation from the interior surfaces of the windows.
An A/C is an apparatus for:
Temperature control and dehumidifier
Air circulation control
Clean air filter and air purification (optional part)
To heat the air, a heater core is adopted as a heat exchanger. The heater core takes in the engine coolant heated by the engine and uses the heat to heat the air from the blower fan, so the temperature of the heater core is low until the coolant temperature becomes high. For this reason, immediately after the engine starts, the heater core doesn’t function as a heater.
To cool the air, an evaporator is adopted as a heat exchanger. When the air conditioner switch is turned on, the compressor begins to operate and sends the refrigerant to the evaporator.
The evaporator is cooled by the refrigerant, which cools the air from the blower fan. Heating depends on engine coolant temperature, but cooling works independently regardless of the engine coolant temperature.
The amount of water in the air increases as the air temperature gets higher, and decreases as the air temperature gets lower.
The air is cooled as it passes the evaporator. Water in the air will be condensed and adheres to the evaporator fins. As a result, the humidity in the vehicle interior is eliminated. The water adhered to the fins becomes dew and is stored in the drain pan.
Finally, it is drained from the vehicle by the drain hose.
The car A/C regulates the temperature by using both a heater core and evaporator, and by adjusting the position of the air mix damper and the water valve. The air mix damper and water valve work with the temperature selector in the control panel.
Recently, the number of models without water valve has been increasing.
Air Circulation Control
1.Natural flow-through ventilator
Intake of external air into the vehicle’s interior due to the air pressure generated by the vehicle’s movement is called natural flow-through ventilation. The distribution of air pressure outside a vehicle as it moves is shown in the figure, with positive pressure generated at some places and negative pressure generated at other places. Thus intake vents are located in places where the air pressure is positive and the exhaust vents are located in places where the air pressure is negative.
2.Forced air ventilator (boost ventilator)
In forced air ventilation systems, an electric fan is used to force air through the vehicle. The air intake vents and exhaust vents are located in the same general areas as the vents in a natural flow-through ventilation system. Ordinarily, this type of ventilation system is used together with another system (such as a heater or A/C).
Clean Air Filter
To purify the intake air, a filter is attached to the intake port of the air conditioner.
When the clean air filter is clogged, it is difficult to take in air, which results in poor air conditioning efficiency. To prevent this, check and replace the clean air filter periodically. The period to check or replace the air filter varies depending on the models or running conditions, so refer to the maintenance schedule.
There are 2 types of the clean air filter: one type removes only dust and the other has deodorizing action with active carbon.
The clean air filter is installed in most recent vehicles, and the filter can easily be removed.
1.What is an air purifier?
An air purifier is a device that removes cigarette smoke, dust, etc., to clean the air of the vehicle interior.
An air purifier consists of a blower fan, blower motor, smoke sensor, amplifier, resistor and filter with active carbon.
The air purifier uses a blower motor to take in air of the vehicle interior, and purifies the air and absorbs odors through a filter with active carbon.
In addition, some models are equipped with a smoke sensor, which detects cigarette smoke and automatically operates the blower motor on “HI.”