How to Take the Chill out of Air-Conditioning Repair


It is another hot day and you turn on your air conditioner, and hot air blows out of the vents. “What’s wrong?” you ask yourself. Well, the possibilities range from a simple fix like a fuse to a serious and expensive repair like a bad evaporator (evaporator leaks are sometimes accompanied by an unusual odor inside the vehicle).

It is crucial to understand that the air-conditioning system is sensitive to many factors that affect its performance. That is because, unlike a very straightforward, obvious repair on your vehicle, the air-conditioning system has components that cannot be determined to be working until the system is ready to be tested. Replacing a damaged compressor may be step one, adding the refrigerant may be step two. But only after the refrigerant is added might the technician discover that the expansion valve is clogged. The point is, you may be led down the path of multiple air-conditioning-related problems as they present themselves and find that you are spending hundreds of dollars with each repair, sometimes resulting in a functioning system and sometimes not. It would be risky for a technician to guarantee that the system will work perfectly after he changes one part, as there are many parts that could be faulty. He should guarantee only the work and the part that he did replace or repair.

Air Conditioning Repair How to Take the Chill out of Air Conditioning Repair

If your A/C is blowing cooler air than the ambient outside temperature, but not cold air, then chances are the fuse is not blown. The compressor, which compresses and transfers refrigerant through the system, is working, and the system may just need to be recharged with refrigerant. Pre-1995 cars used the refrigerant R12, which depletes the earth’s ozone layer. Currently R134a, an environmentally accepted gas, is being used. A technician should check the operating pressure of the system to determine if it is low.

If the A/C is blowing warm air when on the coldest A/C setting, then one of the possibilities is that all the refrigerant in the system has escaped. In any case, when refrigerant has escaped, the leak must be located and repaired to prevent the future escape of the gas. Leaks from the A/C system can be located by a few different means. The most basic way is to visually inspect all the different components, specifically where they connect to a hose or fitting, and look for any wetness around these connections. Oil is mixed with the refrigerant to lubricate the compressor. The leaking refrigerant and oil will leave a wet stain that usually attracts dirt. For instance, if you find a wet and dirty stain on a high-pressure hose, especially next to a connecting point, it’s likely you have located your leak. Another way a technician would determine if there was still a leak would be by evacuating the system. This is done by sucking any and all air or refrigerant out of the lines with a vacuum pump, thereby creating a vacuum. Once the proper vacuum is reached on his vacuum gauge (minus 25-minus 30 lbs.) it is carefully monitored. If the gauge holds the vacuum for a specified period of time (15-20 minutes) the technician knows there are no more leaks. (Some shops prefer to hold the car overnight for checking small leaks.) If it fails to hold the vacuum, he knows there is a leak and can determine by the vacuum loss if the leak is small or large.

The next step to find a leak would be to add refrigerant with a dye additive. This leaves a stain visible with the aid of an ultraviolet light. The stain will reveal any and all leaks. Minor leaks will show traces of dye after two to three hours of continuous usage.

Air Conditioning Repair 1 How to Take the Chill out of Air Conditioning Repair

Aside from leaks, a common cause of A/C failure is a bad compressor. The compressor, which is spun via the air-conditioning belt or serpentine belt (both should be checked periodically to ensure that they are tight and in good condition), compresses the refrigerant and forces it through the system.

If the compressor goes bad it is usually accompanied by a knocking noise. Sometimes the compressor seizes altogether, causing the A/C belt to screech or break. It is important to realize that if your A/C compressor belt breaks and it also controls the water pump, your engine will quickly overheat.

Other kinds of collateral damage can result from a bad compressor. Small particles can break off inside the compressor and then travel and clog other parts in the system, such as the expansion valve, leading to further problems.

A partially blocked orifice tube will prevent your A/C from performing efficiently. Ice, sludge, or debris can form on the orifice tube. This excessive moisture and debris should be vacuum-purged overnight to clean out the system.

Most A/C systems have a built-in sight glass, which is a small see-through glass about a quarter of an inch in diameter. It is used to look for the presence of bubbles while the A/C is working. Bubbles in the sight glass would be an indicator that the system needs to be recharged with refrigerant. Systems that use R134a do not have a sight glass, as the oil in this refrigerant causes a cloudiness that might be mistaken for bubbles, and a technician might then overcharge the system, damaging it.

Air Conditioning Repair 2 How to Take the Chill out of Air Conditioning Repair

Keep in mind that water dripping from the bottom of your vehicle when the A/C is working on hot days is just normal condensation running off the evaporator.

In general, moisture is your A/C system’s enemy number one. If your system has been opened (because of a broken hose or a part temporarily removed) for even a few days, moisture that is present in the air will get in and mix with the refrigerant, forming a corrosive acid. If this is the case, you should replace your receiver-drier (which removes moisture) and evacuate the system before recharging.

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