Air Conditioning Repair
How Air Conditioning Works
A car’s A/C works much in the same way a residential air conditioning system works, but on a much smaller scale. The ﬁrst and most important element is refrigerant. In the case of most vehicles built after the 1990s, the refrigerant of choice is R134a. It’s less damaging to the environment, the ozone layer in particular, than its pre-1990s predecessor, R12 (also known by the brand-name Freon).
A car’s A/C depends on the thermodynamic properties associated with these operating within a closed loop under the correct pressure.
- The thermodynamic properties of refrigerant gases under pressurization is a complex process, but in a nutshell, when refrigerant in its cool liquid form is exposed to warm air, it evaporates into a gas and absorbs or removes heat from the surrounding environment. This occurs in an A/C component in the car known as the evaporator. It’s important to note here that an A/C system doesn’t technically produce cool air, it removes heat from the air via the evaporator, then relies on the car’s blower and air ducts to blow cool air out into the cabin.
- Now that the refrigerant has removed heat from the cabin, the hot refrigerant in gas form then travels to a separate part of the system, where the gas is compressed by the compressor.
- Already heated by absorbing heat through the evaporator, the compression process creates even more heat. To remove this heat and once again cycle cool liquid through the system, the hot refrigerant gas is forced through a series of coils in the condenser, which is similar to a radiator in that it dissipates heat. The pattern of the coils creates a wide surface area in a compact space. Blowing air across this surface (created by the vehicle’s movement or a fan), dissipates the heat, turning the refrigerant gas back into a cool liquid.
- Before the refrigerant can cycle back through the system, any water that may have been created in the process needs to be removed. This is achieved by a component known as a receiver or dryer. Once the water is removed, the refrigerant can start the cycle all over again.
Recharging Air Conditioning Refrigerant
If you've noticed a lack of cooling output by your car's A/C, but components like the blower motor appear to operating correctly, a likely cause is a refrigerant leak in the system. R22 or R134a refrigerant itself never degrades or distengrates if it's in a sealed, pressurized system, so if an A/C system is low on refrigerant, there is almost certainly a leak in hose, connection ﬁtting or A/C system component. Because refrigerant is highly damaging to the ozone layer, it's a car owner's environmental responsibility to diagnose and repair a refrigerant leak as soon as possible.
Once the leak has been located and repaired, the system can then be recharged to ensure it contains the correct amount of refrigerant.
If you've ever visited an auto parts retailer or the auto parts section of a big-box store during the heat of the summer, you've probably noticed DIY refrigerant recharging kits for sale. These kits oﬀer the at-home cost-savings over having a qualiﬁed mechanic recharge the system, but come with certain drawbacks.
First, if you're not repairing the leak that's caused a low refrigerant level in the system, the system will continue to leak. Not only is this bad for the environment, it will eventually necessitate recharging the system again. Second, the refrigerant in your car's A/C system operates under pressurization and correct system pressurization means less wear and tear on system components. A qualiﬁed technician or shop will utilize a more sensitive pressure gauge when recharging the system and ensure it's recharged to manufacturer's speciﬁcations.
Since R22 refrigerant was phased out of production and widespread use by Environmental Protection Agency regulations starting in the 1990s, drivers of older vehicles that use R22 should expect to pay more for refrigerant recharging services. Although R22 is still availble, supply is reduced every year, increasing its cost.