Heating and Air Conditioning: Description and Operation
Description and operationAir conditioning (A/C) system
The A/C system uses principles of thermodynamics to cool passenger compartment of vehicle. Using engine power, compressor compresses gaseous refrigerant into high temperature/high pressure gas. It then pumps this gas into a condenser unit built onto vehicle's radiator. Condenser cools gas, changing it into high pressure, low temperature liquid refrigerant. Liquid then goes to receiver/drier, which first removes any liquid water and then sends liquid to an evaporator in heater unit inside passenger compartment. Evaporator then uses passenger compartment temperature to turn liquid back into a gas, extracting heat from passenger compartment. Gas is then sent back to compressor, and cycle begins again.
A/C relay
A/C relay is an electrical switching box that closes circuit to condenser fan relay and compressor clutch. Relay is controlled by engine control module (ECM) only. If engine coolant exceeds a certain temperature, engine control module (ECM) sends a signal triggering A/C relay and shutting off A/C system. At starting or lighten acceleration, engine control module (ECM) sends a signal triggering A/C relay and shutting off A/C system for five seconds. It is a replaceable item.
Blower
The blower draws in hot passenger compartment air and sends it through evaporator coil. It consists of a blower fan and an electric motor.
Blower motor
Blower motor speed is controlled by blower switch and a resistor assembly in blower unit. When blower switch is in OFF position, motor ground circuit is open and blower motor does not operate. When switch is in first (LO) position, current flow to blower motor is restricted by three resistors in resistor assembly, and blower motor turns at a low speed. Changing blower switch to second (M1), third (M2), or fourth (HI) positions causes successive decreases of circuit resistance, resulting in blower motor speed becoming correspondingly faster.
Compressor assembly
The compressor assembly is primary moving part of air conditioning system. If it fails, there is no compression of refrigerant, and no movement of refrigerant through system. It is located on left side of engine and is connected to engine crankshaft by a drive belt. It consists of compressor, manifold assembly, compressor clutch, and drive pulley.
Compressor clutch
The compressor clutch engages compressor. It is a magnetic unit operated from air conditioning switch in passenger compartment. It is a serviceable, replaceable item.
Condenser
The condenser is mounted in front of radiator. It consists of a series of coils which cool refrigerant. It is a serviceable and replaceable item.
Condenser fan
The condenser fan improves air flow through condenser. Condenser will still have a high volume of air flowing through it even if vehicle is standing still. It is powered by an electric motor connected to condenser fan relay. Condenser fan relay is an electrical switching box that closes circuit to condenser fan.
Evaporator assembly
The blower/evaporator assembly houses blower fan, blower motor, and A/C relay for air conditioner system. It consists of evaporator core and expansion valve.
Evaporator core
The evaporator core is an air cooler and a dehumidifier. As refrigerant enters, it boils, absorbing heat from air being blown through core by heater blower motor. This cools air, which is then directed to passengers through air ducts. As air is cooled, moisture in air condenses on core and is drained off. Result is cold, dry air. Evaporator core is a serviceable, replaceable item.
Expansion valve
The expansion valve allows high pressure liquid to expand as it enters evaporator. By allowing liquid to expand, it will absorb more heat in evaporator. Valve also meters amount of refrigerant entering system to prevent evaporator core from flooding.
Fresh/Recirculation actuator
When fresh/recirculation switch in heater and A/C control panel is pushed, motor in fresh/recirculation actuator assembly moves and its position is not fed back to fresh/recirculation switch.
When desired air fresh/recirculation door position is reached, motor stops.
Heater
Dehumidified air is reheated as it passes through heater core in heater unit. Heater is warmed by engine coolant passing through tubes of heater core. Heat is transferred to core fins and passed off to air flowing past fins. Position of air temperature valve in air conditioning module determines how much of total airflow is permitted to pass through heater. This determines warmth of overall air flow that is sent into passenger compartment.
Hoses and lines
Hoses and lines carry refrigerant between major components of A/C system. Lines are made of metal and are rigid. Hoses are made of flexible rubber and are designed for either high or low pressure. They are replaceable items.
Receiver/Drier
The receiver/drier is located at front power steering oil tank. It receives liquid refrigerant from condenser, removes any water in it, and then sends refrigerant to evaporator. It is a replaceable item.
Service ports
Service ports allow injection or recovery of refrigerant to A/C system. High-pressure service port is mounted in high pressure line coming from receiver/drier. Low- pressure service port is in section of flexible hose that connects evaporator return line to compressor.
Refrigerant
Refrigerant 134a (R-134a) systems
In an effort to avoid use of ozone-depleting CFC refrigerants, Kia Motor Company has introduced a new refrigerant system for this vehicle. This system uses non-CFC-based refrigerant R-134a.
This new type of refrigerant has many of same properties as R-12 and is similar in form and function. R-134a is a hydrofluorocarbon (HFC)-based refrigerant, however, R12 is a chlorofluorocarbon (CFC). With no chlorine atoms in its molecular structure, use of R-134a refrigerant will not have any harmful effects on atmosphere's ozone layer.
Identifying R-134a and R-12 A/C systems
To determine which types of A/C system a particular vehicle has, inspect A/C system's major components and refrigerant lines for special tags. If system has yellow R134a "NON-CFC" tags, it is an R-134a system and uses R-134a refrigerant. If there are no special R-134a "NON CFC" tags on A/C system components or lines, system uses R-12. R-134a systems can also be identified by brown colored O-rings (HNBR) used throughout A/C system.
CAUTION: Do not add R-12 refrigerant to an A/C system that requires use of R-134a refrigerant. Do not add R-134a refrigerant to an A/C system that requires use of R- 12 refrigerant. These two types of refrigerant should never be mixed. Doing so may cause damage to A/C system.
R-134a system components
The major components of R-134a A/C system are similar to those used previously on R-12 systems. R-12 and R134a components are similar in design and function. As a result, all Removal and Installation procedures outlined
for R-12 components can be used for R-134a components.
(Refer to operating instructions of your refrigerant recovery/recycling/charging station for proper procedures.)