Why Does Your Air Conditioning Need Recharging?

CARS.COM — On hot, sunny days, few things are more frustrating than having to ride around in a car with a non-functional cooling system. If your car's air-conditioning system blows only warm air on hot days, it's probably because it is low on refrigerant, and the most likely cause is a leak somewhere in the system.

Let's take a closer look at what causes car air conditioners to blow warm air and when car cooling systems may need to be recharged.

Related: More Maintenance Coverage

"Topping Off" Your Car's AC System Is Not Necessary

Though many car owners think they need to recharge or "top off" their air-conditioning system with refrigerant on a regular or annual basis, that's not the case. An AC system is a closed system, and if there are no problems, coolant is not consumed by the vehicle, nor does it escape. Unless your auto's AC is in need of repair, there is no need to "top off" the system. If the air conditioning stops working but the fan continues to blow warm air, a leak in a hose, connector or other part of the system is probably the culprit.

During the winter, you may notice that the defroster isn't clearing fogged-up windows; that is also a sign that you have a leak. Most defrosters engage the air conditioning to dehumidify the air. Problems with your car's AC may also signify compressor on condenser troubles that require professional repair. Auto ACs are complex systems, and there are numerous things that can go wrong. This is especially true of air conditioners in older vehicles.

If there is a leak in a hose or anywhere else in the AC, the system on most modern vehicles is designed to shut down once the refrigerant level drops to a certain level in order to prevent damage to the air-conditioning compressor. The compressor pressurizes the refrigerant and keeps it flowing throughout the system. When there is not enough refrigerant in the AC, serious compressor damage may occur. Generally speaking, compressor repair is quite expensive and best to avoid whenever possible.

Note that we are talking about "refrigerant," not Freon, the brand name for a type of refrigerant that is no longer manufactured in the U.S. because it can damage the ozone layer. Contemporary vehicles use a refrigerant known as R-134. R-134a refrigerant may also be used in some vehicles.

If Your Car Air Conditioner Needs to Be Topped Off

The EPA provides helpful information for consumers about whether they should have the air conditioner in their car topped off with refrigerant or evacuated and recharged, found here. The EPA notes that a repair shop (or a do-it-yourselfer) can't tell precisely how much refrigerant is in the system without the proper equipment — gauges to measure how much pressure is in the system — so how much they add while topping off the system is largely a judgment call.

By performing a complete evacuation and recharge (a more expensive procedure and one that should be done by a professional), the EPA advises, the repair shop will be able to test the complete system and recharge it with the precise amount of refrigerant recommended by the vehicle manufacturer. The EPA adds that there usually is no reason to clean the system unless it is opened up, as when you need to check for leaks or other problems.

When is it time to add or replace the refrigerant? You could be proactive and have it done before you experience problems, but you shouldn't need that more often than every few years at most. If your air conditioning is losing its potency even after topping it off, then you probably have a leak. But if you stay as a cool as a cucumber on the hottest days, you could just leave well enough alone. The air conditioner obviously has enough refrigerant.

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