Air Conditioning Not Cold - Why Air Isn't Good For Car's AC

Over time many car air conditioning systems may not cool as well as they used to. At the beginning of summer many car owners make this discovery. The number one cause of an AC system not cooling well is low refrigerant. But when should a car's AC system be completely evacuated and recharged? As a rule, anytime the AC system has been opened for service. This could be when a leaky hose, evaporator or any other failed component has been replaced. Remember that if there is any Freon in the system at all, it needs to be recovered and recycled by an AC machine. When a component is replaced, the drier (AKA Accumulator) should be replaced also. The drier has desiccant which absorbs moisture in a system. It's effectiveness is diminished after it is exposed to the atmosphere for any length of time.

Also the lifetime of a drier is said to be about two years in a closed system. In rare cases if the drier is very old, the desiccant bag can break and contaminate the AC system. I once worked on an old Ford LTD, I think it was a 1978 with the drier mounted on the condenser (in front of the radiator). A previous repair shop put twice the specified amount of R-12 refrigerant in the system to get it to cool some. I found that the condenser was restricted due to the desiccant bag breaking. The drying agent was released to flow into the condenser restricting it severely. The over-charge of R-12 refrigerant helped to force some freon through the system. After flushing the condenser, I replaced the drier and used a vacuum pump to vacuum the system down fully. I charged the system with the correct amount of oil and refrigerant - my FATHER IN-LAW was very happy!

After any repair has been made, an A/C vacuum pump (hooked to gauges) should be used to vacuum the system down before recharging. For an AC system to cool properly and at it's coolest, the system needs to be completely void of any AIR. If air is in the system it will be pumped by the AC compressor along with 134A throughout the components. But instead of the refrigerant in the system transferring the heat and cold as it is designed, the air that's mixed in will cause less efficient operation. So when a car's AC isn't as cold as it should be, many professional auto techs will evacuate and recharge the system to help insure air is removed and the proper amount of refrigerant is in the system.

Evacuate and Recharge a System

1. Insure a proper charge.


2. Add correct amount of oil.


3. Remove moisture.


4. Remove air.


5. Only approved way to to remove refrigerant from a system is with an AC recovery machine.