Auto Repair Q&A



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Parts Replacement on An Air Conditioning System

Compression test gauge

Sometimes, things go wrong on your car's air conditioning system. The AC system is simple in its operation, but can have some complex repair issues due to the legalities of the refrigerants involved.

Be aware that the following information can be used by DIY mechanics, but that there are strict laws regulating automotive air conditioning service and those working on them. Fines can result if you are not certified to perform this work.

Evacuating (removing) the refrigerant from your air conditioning system requires special equipment and knowledge. In many areas, however, it is legal to have a shop remove the refrigerant so that you can work on the system yourself before paying the technician to refill (recharge) the AC system. In other areas, you are not allowed to work on your AC system at all without certification and specialized tools. In those places where you can DIY the the work, however, this information will prove useful.

The most common failures on an AC system are in the closed loop itself through leaks or the compressor and/or its clutch. Replacement of the compressor is relatively straightforward, though removing and re-installing or replacing the pulley and its clutch can be tricky. Some parts stores and make/model of car will have a pulley and clutch that's separate from the compressor. Others come as one unit without the possibility of replacing just one or the other. You may need a special tool to pull the clutch from the compressor in the former case. It's recommended that you use the proper tool or have a professional do it as it's easy to break the pulley and clutch if you do it improperly.

Another often overlooked item to replace in the AC system is the receiver/dryer (or accumulator). If the AC has been exposed to outside air or evacuated for some time, it's likely that moisture and debris have accumulated in the receiver/dryer. This is what they're made to accomplish, but they can become full or clogged with exposure. Replacing them is relatively easy and is always an added bonus to your AC system's operation whether the replacement was required or not. These are generally low-cost units and are very easy to replace, so it's recommended that you do so if you're working on the AC system already. If you do other repairs and don't replace the dryer, you could find yourself paying for another evacuation and recharge because those units aren't working properly. You could also see more failures in the system down the line.

Also remember that when you replace parts in the AC system, there may be a prescribed amount of refrigerant oil to be added. Most parts stores and suppliers sell their AC system parts with the prescribed amount of oil already in the part to be installed, saving you this hassle. Otherwise, you'll need to become familiar with the measurements involved.

Finally, recharging the AC system is not as simple as hooking up a can of replacement refrigerant from the parts store and filling the lines. The lines must be evacuated completely (under vacuum), the closed loop checked for leaks, and the right amount of the right kind of refrigerant added to the right place in the system. This requires specialized tools and training. Something a home mechanic is not very likely to have or even have access to. Laws also regulate who can and cannot perform this work legally. So bear that in mind.

Most AC system parts replacements are pretty straightforward. They usually require a couple of gaskets (usually supplied with the part) and a wrench to disconnect the old from the lines and replace it with the new part.