1. HIGHLIGHTS
Preamble
Functions of Car AC
Automobile AC Usage and
Safety
Car Care
Preventing Problems
Common Problems in Car AC &
Solutions
Maintenance Recommendations
2. PREAMBLE
The motor vehicle, one of man’s greatest inventions,
provide comfort and relief as it helps in movement of
persons, goods and services from one location to another.
The vehicles operate under a wide range of temperature
conditions which may not be comfortable for humans. The
need to maintain comfort in these vehicles, led to the
invention of Motor Vehicle Air Conditioning (MVAC) also
known as Automotive Air Conditioning or Automotive
Heating, Ventilation and Air Conditioning (HVAC) and the
more recent Climate Control Systems on many high end
automobiles in use today.
These systems provide comfort cooling for
passengers in cars, trucks, buses, planes, trains, etc.
3. PREAMBLE
Air Conditioner in cars is unique due to the fact that
they are used in widely varying ambient conditions,
likelihood of accidents, and the location of a part of
the system – the evaporator – inside the passenger
compartment.
An air conditioner has become a
staple in most vehicles these days.
They greatly impact a car’s resale
value.
An air conditioner is a device that helps to regulate
the temperature, humidity and purity of air in a living
space.
5. DEFINITIONS
Refrigerant: A refrigerant is a working fluid used in the refrigeration
cycle of air conditioning systems and heat pumps.
Compressor: The pump in the A/C system to keep the refrigerant and
lubricating oil circulating, and to increase the refrigerant pressure
and thus temperature.
Condenser: The Condenser function is to act as a heat exchanger and
allow heat to flow from the hot refrigerant to the cooler outside air.
Evaporator: Functions as heat exchanger allowing cool air into the
passenger compartment.
Expansion Valve: Provides throttling (control) of the pressure and
amount of refrigerant entering the evaporator.
Receiver (Filter) Drier: Acts as a particle filter, refrigerant storage
container and most importantly moisture absorber.
Orifice Tube: A fine restriction causes pressure and temperature drop in
refrigerant entering the evaporator.
Condensate: Moisture contained in the warm air flowing through the
evaporator will condense. Can be seen under the car forming
puddles
6. DEFINITIONS
Evacuation (Vacuum): Subjecting a refrigeration system to pressures
below ATM.
“O” Rings: Rubber compound used for A/C system joints, fittings and
components.
Hoses: Flexible pipework for connecting AC system components.
Charging Ports: Enable the A/C system to be serviced and tested whilst
under pressure
Ozone Depletion Potential (ODP): of a chemical compound is the
relative amount of degradation to the ozone layer it can cause.
Global Warming Potential (GWP): is the heat absorbed by any
greenhouse gas in the atmosphere, as a multiple of the heat that
would be absorbed by the same mass of carbon dioxide (CO2).
Refrigerant Reclamation: is the act of processing used refrigerant gas
which has previously been used in some type of refrigeration loop
such that it meets specifications for new refrigerant gas.
ASHRAE: An industry standards organization.
Slugging: An unwanted condition in which the compressor is supplied
with liquid refrigerant.
Editor's Notes
Having a working air conditioner unit is especially important on hot days.
Refrigerant types: CFC (R12), HCFC (R22), HFC (R134a, R404a, R407a, R410a), HC (R290, R600) HFO (R1234yf), CO2 (R744)
Refrigerants in most cases undergo a repeated phase transition from a liquid to a gas and back again. Refrigerants are heavily regulated due to their toxicity, flammability and the contribution of CFC and HCFC refrigerants to ozone depletion and that of HFC refrigerants to climate change.
Desirable Refrigerant properties:
The ideal refrigerant would be: non-corrosive, non-toxic, non-flammable, with no ozone depletion and global warming potential. It should preferably be natural with well-studied and low environmental impact. It also needs to have: a boiling point that is somewhat below the target temperature (although boiling point can be adjusted by adjusting the pressure appropriately), a high heat of vaporization, a moderate density in liquid form, a relatively high density in gaseous form (which can also be adjusted by setting pressure appropriately), and a high critical temperature. Extremely high pressures should be avoided. Newer refrigerants address the issue of the damage that CFCs caused to the ozone layer and the contribution that HCFCs make to climate change, but some do raise issues relating to toxicity and / or flammability.
Compressor types: The internal design could be Piston, Scroll, Wobble plate, Variable stroke or Vane
Receiver Drier: Moisture, temperature and R134a causes hydrofluoric and hydrochloric acid. The silica gel beads (desiccant) located in the FDR absorb small quantities of moisture thus preventing acid establishment.
TXV ensures complete evaporation of liquid refrigerant
Vacuum usually to -29.9 in HG (-100Kpa , -1bar, -14.5psi,
“O” Rings: Rubber compound used for A/C system joints, fittings and components is a hydrogenated nitrile butadiene rubber (HNBR) and identified by the colour green.
Standard J639: Safety Standards for Motor Vehicle Refrigerant Vapor Compression Systems
This standard covers any vehicle with a MAC system using a belt or electric motor driven compressor.
(ASHRAE) The American Society of Heating, Refrigerating and Air-Conditioning Engineers
