How A/C Works

At the inception of the invention of air conditioning, authorities in the field stipulated that an air conditioning system must perform the following functions;

  •     control temperature
  •     control humidity
  •     control air circulation and ventilation
  •     cleanse the air

Essentially, air conditioning works by reducing moisture in the air. All refrigeration works upon this same principle whether it is cooling for a vehicle, a home or a refrigerator. When you turn on the A/C in your vehicle or in your home it uses energy; whether fuel in your car or electricity in your home to remove moisture from the air, thereby reducing the temperature.

The primary functions that occur during air conditioning are;

  • Evaporation
  • Condensation
  • Compression
  • Expansion

Hard tubing and flexible hoses connect all the actual components of the air conditioning system in your car. Evaporation and condensation, expansion and compression all working together are the physics of why it works.


How the A/C System Works in Your Vehicle

A/C Fluid

The fluid that passes through the entire A/C system is the refrigerant. The refrigerant can evaporate at a low temperature, and then condense again at a higher pressure.  All cars built after 1996 use a non-CFC fluid called R-134A or R-134 which is deemed environmentally friendly. Because the working fluid gets both very hot and very cold, it is important to keep moisture out of the system, as ice forming in the compressor can damage it.


The compressor is the work horse of the air conditioning system, powered by a drive belt connected to the crankshaft of the engine. When the air conditioning system is turned on, the compressor pumps refrigerant vapor under high pressure to the condenser. The compressor then draws in the low-pressure refrigerant vapor to start another refrigeration cycle. The refrigeration cycle then runs continuously, and is regulated by the setting of the expansion valve.

The compressor takes low pressure, gaseous, r-134a and compresses it which generates heat. Then send that heat to the condenser, where the heat is dissipated to the outside. After the condenser, liquid refrigerant travels to the evaporator, located inside the passenger compartment, where it is allowed to expand, removing heat and cooling the evaporator. The fan directs air over the evaporator, then out the air vents into the car.


The condenser and evaporator are, essentially, two radiators connected in a loop.  The condenser is a device used to change the high-pressure refrigerant vapor into a liquid. It is mounted in front of the engine’s radiator, and it looks very similar to a radiator. The vapor is condensed to a liquid because of the high pressure that is driving it in, and this generates a great deal of heat. The heat is then in turn removed from the condenser by air flowing through the condenser on the outside.


The evaporator is another device that looks similar to a car radiator. It has tubes and fins and is usually mounted inside the passenger compartment behind the fascia above the footwell. As the cold low-pressure refrigerant is passed into the evaporator, it vaporizes and absorbs heat from the air in the passenger compartment. The blower fan inside the passenger compartment pushes air over the outside of the evaporator, so cold air is circulated inside the car. On the ‘air-side’ of the evaporator, the moisture in the air is reduced, and the ‘condensate’ is collected and drained away.


The now liquid refrigerant moves to the receiver-dryer. This is a small reservoir vessel for the liquid refrigerant, and removes any moisture that may have leaked into the refrigerant. Moisture in the system causes havoc, with ice crystals causing blockages and mechanical damage.

Expansion Valve

The pressurized refrigerant flows from the receiver-drier to the expansion valve. The valve removes pressure from the liquid refrigerant so that it can expand and become refrigerant vapor in the evaporator.

Auto Air Conditioning Problems

Your vehicle’s A/C may not be working properly for many reasons. Here are the top 3 reasons you’re car’s air conditioning may not be working properly;

  1. Moisture or Dirt in Tubing from a Leak

The air conditioning system is originally built to maintain tight seals on all tubing.  If any of the tubing or seals crack or break then air, moisture and dirt can infiltrate the A/C system. This can cause the lines to freeze. This will block refrigerant flow from being able to cool your car. You can tell this has happened to your car if when you turn the A/C on sometimes warm air comes out of the vents alternating intermittently with cool air, then back to warm and so on.

  1. Moisture in the A/C System from A/C Fluid Refill

When topping off the R-134a fluid moisture can enter in if extreme care isn’t taken. This is one major reason to have you’re A/C fluid refilled by a professional instead of doing it yourself.

  1. Accident Caused A/C Not to Work

An accident often causes a leak in a valve or tube which allows moisture and dirt into the A/C system.


If you’re A/C is not working properly it is probably due to one of these top 3 A/C failure reasons. A leak check can locate exactly where the leak is occurring so that the proper parts can be replaced in order to restore the full function of your air conditioning system. Our air conditioning diagnostics will find the problem so we can repair your air conditioning for the best price.

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