How Do I Repair My Car’s AC?

Repairing your car’s AC can be a complicated or simple project depending on what’s wrong with it.  With most things in your vehicle, a better understanding of the components and what they do will help you diagnose the problem and determine the best and most inexpensive solution.  The air conditioning system in modern vehicles has 5 major components that are connected by hoses or pipes.

Air Conditioner System Components:

1. Compressor
2. Condenser
3. Receiver or Dryer
4. Expansion Valve
5. Evaporator

The AC system in your car all starts with the compressor.  The compressor is usually bolted to the front of your engine and powered by a belt connected to the crank pulley on your motor.  Even though the belt is always moving around the AC compressor pulley, it also has a clutch that can engage the pulley to compress refrigerant when the AC is turned on, or the clutch can disengage allowing the compressor to rest, increasing fuel mileage and the life of your AC system.  An AC compressor may fail due to a lack of lubrication in the refrigerant, the clutch may wear out or it may develop a leak.  You can check for a failed clutch by watching the center of the compressor pulley while the air conditioner is turned on and the engine is running, while also testing the system pressure to verify the presence of the right amount of refrigerant.  Remember a broken AC compressor clutch may be a mechanical or an electrical failure.

The warm compressed refrigerant is then transferred by a hose or pipe to the condenser.  The condenser is usually near the front of the vehicle because it needs ambient air to pass through it to cool the warm compressed refrigerant to an ambient temperature liquid.  Since the condenser is at the front of your vehicle it’s most likely failure is a leak, either due to a failed O-ring where one of the refrigerant lines enters or exits, or due to road debris puncturing it.

After the refrigerant is a cooled to an ambient temperature by the condenser, it is passed through the receiver or dryer.  This device holds a certain amount of refrigerant and accumulates it before it passes to the rest of the system.  This accumulation process ensures that all of the refrigerant is now a liquid instead of a gas and is safe to continue through the rest of the system.  The dryer also can help filter out any contamination that may be in your air conditioning system.

The refrigerant then travels on to the expansion valve which is the secret to the air conditioning system.  At the expansion valve, the ambient temperature high pressure refrigerant is allowed to expand very quickly taking advantage of the Joule-Thompson effect.  This scientific principle states that, as a gas, it is allowed to expand quicklyso the temperature of that gas will drop significantly.  This cold refrigerant can then go on to cool your vehicle.  Expansion valves usually fail by becoming clogged with small particles from your air conditioning system.  The orifices are so small you will not be able to unclog the valve, so your only option is to replace it.

The cold refrigerant then travels to the last piece of equipment in the air conditioning system of your vehicle, the evaporator.  The evaporator is located in the air ducts, usually just before the heater core.  The cooled refrigerant cools the evaporator, which in turn can cool the air in the cabin of your vehicle.  Like the condenser, the evaporator is very delicate and usually fails due to a leak in one of the lines or a puncture in the evaporator itself.  Since the evaporator is in the cabin of your vehicle, it is usually well protected and rarely fails due to a puncture.

Since your air conditioning system uses clean refrigerant and is a closed system, the compressor, dryer and expansion valve are subject to very little debris or harsh environments and don’t often fail.  When they do, usually the only solution is to replace the component in its entirety.  Depending on its location and your skill as a mechanic, you should consider having a professional complete the replacement.  Determining which component has failed can usually be accomplished by checking the pressures at different points around the system to determine what has failed or where the clog is located.

What is the most common AC failure?

The most common failure in an air conditioning system is a refrigerant leak, often at the condenser, but is possible at any of the connections from a hose to a pipe or from component to component.  If the leak is severe, it may be necessary to replace the hose, or condenser or evaporator but in most cases these leaks can be sealed simply and quickly by using BlueDevil Red Angel.  BlueDevil Red Angel A/C Stop Leak is specially formulated to seal the leaks in your system without damaging any of the delicate components.  It is not a particulate sealer so it will not clog your expansion valve.  BlueDevil Red Angel A/C Stop Leak will remain in your air conditioning system until it comes to leak point where the difference in temperature due to the leak will cause it to activate, causing a chemical weld to form quickly and sealing your leak.  Simply add the correct amount of refrigerant to your system and enjoy cold air all summer long.