Car A / C problems are one of the most misdiagnosed issues when it comes to auto repairs. The number one problem that auto technicians have to troubleshoot and find, is "why the AC is NOT blowing cold." When the car's air conditioner has this problem, it can be caused by one of many things. The most common cause of the air conditioning blowing warm air is a refrigerant leak. No matter if the AC system uses R12, R134A or any other refrigerant; The theory of operation is the same. They all require a full charge of refrigerant to work properly. Refrigerant can leak from any of the components in the system. A car's AC components are located in different areas in the vehicle – not all together in an easily replaceable unit like a house AC "window unit." It is critical that the failed part is located and replaced to insure a long lasting repair.
Look for Obvious Signs of Leaks
The first thing that anyone can do, mechanic or not is look for an obvious sign of a refrigerant leak. Most systems will have UV dye in the system that is neon yellowish green. It can be seen easier with a black light, but it can still be visible to the naked eye also. If there is no dye in the system, the leak may trickle out clear oil. Inspect all of the components starting at the service ports. Look at the service fittings for leaks and all of the hoses. Follow the lines each direction paying particularly close attention to the metal ferrules that connect the rubber hoses to the metal lines. Check for any lines that may have made contact with other components under the hood and may have vibrated and caused a hole to be rubbed through. The condenser is located in front of the radiator, check every square inch for signs of impact damage that may have caused a leak. Even without a rock or something hitting the condenser, there could still be a leak – look for evidence of any oil residue especially on all four corners.
Detect a Hard to Find Leak – Troubleshooting
After a quick visual inspection for leaks of the components that are under the hood, it may be necessary to look a little further with the help of a refrigerant leak detector to troubleshoot the problem. If the system has little oil in it, there may not be much residual to see from a leak. With a freon leak detector, the leak can be detected even if it is a very slow one. Go over all of the components as mentioned before, but this time with the electronic leak detector. The evaporator is the component in the passenger compartment, which is NOT visible like the other components from under the hood. Leaks from the evaporator can sometimes be detected through the vents. A common place to detect an evaporator leak is from the evaporator drain. Refrigerant is heavier than air, so it will naturally go out the water drain for the evaporator. Be careful NOT to allow water to enter the tip of the leak detector or it may be damaged.