Automotive Air Conditioning

After a wonderful and wet spring, summer is just around the corner. At this time of the year, people often ask us how much it costs to fix the AC in their car. This is a great question, and I’ve revised my explanation a bit in hopes of demystifying the process. In the past, vehicles used the refrigerant R-12, aka Freon. Since 1994, vehicles have been using the refrigerant R-134a. Most recently, vehicles are being sold with the refrigerant 1234-YF. All that aside, the core components of the AC system are very similar and consist of a compressor, condenser, evaporator, orifice/expansion valve, and a filter. The heat pump at your house works in a similar way. In the most general sense, the system works based upon phase changes of the refrigerant. The compressor, or pump, is the heart of the system and pumps the gaseous refrigerant through a closed cycle of pressure and phase changes. As the refrigerant evaporates in the evaporator, it is extremely cold and readily absorbs heat. As air is moved across the evaporator in the depths of your car’s dash, it quickly becomes cooled. If the compressor fails, it can often pump very small pieces of itself through-out the system, thus causing plugging, contamination, and failure of other parts. It’s also helpful to know that in many cases, but not all, an inoperative air conditioning system is the result of the refrigerant (in a gaseous state) having leaked out. Once the refrigerant has leaked out, damage can occur. Now one problem has become two problems – the leak and the damaged parts.

Now, back to testing. The AC system first needs to be tested to determine if it’s low. This testing is commonly referred to as an “AC Service.” During the AC service, the technician uses a specialty tool to determine how much refrigerant is in the system, and then fills the system to proper capacity if it’s low. It’s imperative this step be performed first because the system has limited self-protection devices which prevent it from operating if it’s grossly under-filled or over-filled. Once the system is filled properly, the technician can then test it for correct operation. As mentioned earlier, air conditioning works based on the principles of pressure and the phase-changes of the refrigerant. The system must be air-tight and free of contamination. Also, without a properly functioning cooling system for the engine (radiator, thermostat, etc.), the AC system can’t work as designed. Recall from my past columns that many systems in vehicles are connected and work together-ugh! It becomes more clear as I write just how complex this can be to explain to a driver. Assuming the system is just a bit low on refrigerant, the technician can install a bit of UV dye into the system, and then use a black light to determine the source of the leak. Once all this testing is complete, the shop can give the customer an accurate estimate on the cost to repair the leak and bring the system back to health. This is the best-case scenario. If the system suffers from a major component failure, the story becomes more complicated and the cost rises. It is critical repairs be performed by a certified and licensed professional, and quality parts must be used. There’s no savings by using cheaper parts, as they can fail prematurely and damage other components in the system. A professional shop can help you through this difficult process, and keep you cool through the summer!

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