Q: What Causes Leaks in a Car's AC System?

Automotive air conditioning (AC) is a closed loop system comprised of four main mechanical parts: the compressor, condenser, evaporator, and depending on system design, receiver drier or accumulator. Refrigerant is circulated through these components with the refrigerant pressure and temperature controlled by, depending on system design, the expansion valve or orifice tube. The evaporator and condenser appear similar to radiators.

The evaporator is the part in the car’s dash that air blows through to have the heat removed and provide interior cold air. The refrigerant leaves the evaporator and goes to the condenser (in front of the car’s radiator) where heat is removed and the refrigerant changes back to a liquid, then goes to the compressor where the pressure is raised, and finally to the accumulator or receiver-drier, which are essentially holding tanks for the refrigerant. The refrigerant is then metered through the orifice tube or expansion valve and undergoes a pressure drop, causing a temperature drop, and then back to the evaporator where the cycle repeats.

These parts are connected with a system of metal pipes and rubber hoses which are sealed to the actual components with o-rings and crimps on the rubber hoses where they attach to the metal pipes. Provided there hasn’t been any physical damage to any parts or connections in the system, the o-rings and crimps are the places where “spontaneous” leaks develop. There are no regular preventative maintenance steps that can be taken to help keep these leaks from happening. Time will cause these leaks to occur, but sealing has come a long way in the last 30 years, so there should be little issue with refrigerant loss in these areas.

If your car does experience that the AC does not blow cold air](https://www.yourmechanic.com/article/why-won-t-my-ac-blow-cold-air), the solution is to temporarily recharge the system and find out where the refrigerant leak is, using an electronic leak detector if the area is not readily visible, and make permanent repairs. Adding refrigerant is only a temporary fix (since the leak hasn’t been repaired) and may not be legal in some states, since some refrigerants are damaging to the ozone layer and are regulated substances. There may be other issues causing the air conditioning not to blow cold, such as a compressor that won’t engage because of electrical problems. Air conditioning repairs and troubleshooting should be entrusted to a qualified and licensed mechanic, since these repairs require specialized training and equipment, and in some areas, a license to handle refrigerant.