If your car's air-conditioning system feels more like a heater, the culprit could be low refrigerant which can escape your system over time. If your system is operating normally (no strange noises or hissing sounds) but is only blowing hot air, it’s likely your vehicle is low on refrigerant and in need of a recharge. Most modern vehicles are designed to shut down the air conditioning system once the refrigerant level drops too low to prevent damage to the compressor.
The problem isn’t confined only to the summertime; you will also see the affects in the winter when the snow starts to fly. You’ll notice that the defroster isn't doing its job of clearing the foggy windows because most engage the air conditioning to dehumidify the air.
By performing a complete evacuation and recharge 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. This needs to be done by a professional who has the necessary equipment to properly measure your refrigerant levels and ensure your system doesn’t get overfilled which could cause more complex (and expensive) problems. According to the EPA , you 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.
The EPA provides helpful information for consumers about whether they should have their air conditioner topped off with refrigerant or evacuated and recharged, foundhere. They also add that usually there is no reason to clean the system unless it is opened up, such as to check for leaks or other problems.
A regular or annual “top off” of your refrigerant isn’t necessary as some vehicle owners may believe. 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 the most. If you top it off or recharge your air conditioning and it’s still losing its cool, you may have a leak in the system. If you stay cool and comfortable on your commute, even on the hottest days, just leave well enough alone. The air conditioner obviously has enough refrigerant.