How Your Car's Heating and Air Conditioning System Works

Most of us have become accustomed to the comfort provided by our vehicles' heating and air conditioning system. During the cold months, warm air keeps the chill at bay. During the warmer months, the A/C produces cool air to make the driving experience more comfortable.

Like most auto parts and systems, the heater and air conditioner work without our thinking about them. Unfortunately, they do suffer wear and tear. They can break down for a variety of reasons, and fail to perform their respective jobs.

The technology used to design your vehicle's heater and A/C has evolved over the last several decades. But problems can still occur. In this article, you'll discover how the various components work together to ensure your drive is as comfortable as possible. We'll then take a look at a few issues you may experience down the road.

The Job Of The Compressor

Attached to the side of your car's engine is a component called the compressor. It is a pump that is responsible for compressing refrigerant (e.g. R-134a, Freon, etc.) and sending it to another component called the condenser (described below). In order to fulfill this responsibility, the compressor intakes low-pressure gas from a part called the evaporator. The compressor pressurizes the gas - heating it in the process - before sending it through the system.

The Condenser And Expansion Valve

Your A/C system's condenser appears similar to your cooling system's radiator. Moreover, it works in a similar manner. Once the high-temperature, pressurized gas from the compressor reaches the condenser, it undergoes a process through which heat is removed from it. During this process, the refrigerant gas is turned into pressurized liquid before it leaves the condenser on its way to the expansion valve.

The expansion valve regulates the amount of refrigerant that reaches the evaporator (described below). When you modify the temperature control in your vehicle's cabin, you are adjusting the setting of this component. The higher the temperature setting, the less refrigerant that is allowed to pass through to the evaporator.

Evaporator

Your air conditioner's evaporator has a few responsibilities. First, it is tasked with removing heat from within the cabin of your car. Second, it removes moisture from the air that leaves it and passes through the vents.

By the time the liquid refrigerant arrives from the expansion valve, much of its pressure has dissipated. It enters the evaporator where it is dehumidified prior to its release. The refrigerant then leaves the evaporator and travels back to the compressor to start its journey over. Meanwhile, cold air is blown through your car's vents with a blower motor.

Potential Problems That Can Develop

The most common problems drivers experience with their car's heating and air conditioner system include a lack of cold air, intermittent cooling performance, and noise and odor. Lack of cold air is usually due to a lack of refrigerant. This implies there is a leak from the seals or hoses somewhere in the A/C system. Finding such leaks is best left to a trained mechanic who has the necessary equipment.

Intermittent cooling is often attributable to an obstruction caused by moisture. Finding the obstruction, similar to locating a refrigerant leak, can be challenging unless you have access to the proper diagnostic equipment. The problem may also be triggered by an electrical failure that prevents the compressor clutch from engaging. If the clutch fails to engage, the compressor will not work.

If you hear your car's A/C system making excess noise, have a mechanic check the compressor. There's a high likelihood the component is about to fail, and will need to be replaced. If you smell a musty odor coming from the vents, mold has likely grown on the evaporator. This occurs because moisture collects on the evaporator's surface (recall that the component dehumidifies the liquid refrigerant). Don't ignore the odor. Have the mold cleared out.

The heating and air conditioning system of your vehicle should operate without incident for years. When problems occur, however, the repairs are best left to a mechanic.