Imagine you have someplace to be and it’s a hot, steamy summer day. You don’t want to arrive a sweaty, wind-blown mess, so you turn on one of the marvels of modern automotive design: the air conditioner. It’s estimated that more than 99 percent of all new cars in the United States have A/C.
So how does your car or truck produce that wonderful cool air at the push of a button? First of all, air conditioning works on two principles: 1. Heat goes to cold (a cold substance attracts and absorbs heat); and 2. Vapors get hot when compressed and get cold when expanded. In the air conditioning world, pressure and temperature are virtually the same thing–30 PSI (pounds per square inch) is roughly equal to 30 degrees Fahrenheit.
Now you’re ready for a step-by-step explanation of how it all comes together!
Step 1: The compressor is the power unit of the A/C system. It is powered by a drive belt connected to the engine’s crankshaft. When the A/C system is turned on, the compressor compresses the refrigerant, known as freon, creating a high-pressure, hot vapor that it sends on to the condenser.
Step 2: The condenser is a device used to change the high-pressure refrigerant vapor to a liquid. It is mounted ahead of the engine’s radiator, and it looks very similar to a radiator with its parallel tubing and tiny cooling fins. If you look through the grille of a car and see what you think is a radiator, it is most likely the condenser. As the car moves, air flowing through the condenser removes heat from the refrigerant, condensing it to a liquid state.
Step 3: Refrigerant moves to the receiver-drier. This is the storage tank for the liquid refrigerant. It also removes moisture from the refrigerant. Moisture in the system can freeze and then act similarly to cholesterol in the human blood stream, causing blockage.
Step 4: As the compressor continues to pressurize the system, liquid refrigerant under high pressure is circulated from the receiver-drier to the thermostatic expansion valve. The valve is actually an orifice. The expansion process, hence the name “expansion valve,” occurs when the refrigerant passing through the orifice suddenly expands, lowering the pressure from around 300 PSI to around 30 PSI, or 30 degrees.
Step 5: The evaporator is very similar to the condenser, except in reverse. It consists of tubes and fins and is usually mounted inside the passenger compartment. As the cold low-pressure refrigerant is released into the evaporator, it vaporizes as a result of absorbing heat from the air in the passenger compartment. As hot air is blown through the evaporator by the fan, the cold evaporator surface absorbs heat and cooled air will be available for the occupants of the vehicle.
Step 6: The heat-laden, low-pressure refrigerant vapor is then drawn into the compressor to start another refrigeration cycle.
Occasionally A/C systems can go on the blink. If you see any of these symptoms, bring your vehicle in for an A/C check:
- The air conditioning won’t blow any cold air.
- The air that is blowing is weak.
- There is a strange odor in the system when you turn it on.
- The car stalls or idles roughly when the A/C is on.
- The windows fog up and won’t clear up.
- The top and side vents or the defroster aren’t working.
At CARS of America, we are all about preventative maintenance. A problem we frequently see, being in the cottonwood capital of America, is a blanket of tree fuzz filling up the void between the radiator and condenser. It restricts air flow, diminishing the air conditioner’s ability to cool the interior and the radiator’s ability to cool the engine. This condition can cause overheating and damage to the engine and/or air conditioner. To prevent this condition from occurring, we inspect that area whenever your vehicle comes in for service at this time of year. On most cars, cleaning is a relatively minor disassembly process that takes less than an hour.
A/C not working right? Give CARS of America a call at 847-724-6724 or schedule an appointment.