Most of us can't imagine what it was like not to have air conditioning, defrosters or  heat in our vehicles, that is until the HVAC system quits working. 

HVAC systems fail to work for three basic reasons: electrically, mechanically or leaks. Electrical failures may not allow the compressor to engage or the electronic controls or blowers to operate properly. Mechanical part failures or breakdown of controls, clutches, motors, pumps or compressors all cause the system to quit operating.  And leaks of refrigerant or coolant(s) from the system will cause the system to not perform properly or shut down completely. It takes a well trained person to determine which problem (or set of problems) is preventing the HVAC system from working.  The most basic components that make up the HVAC system are the compressor, condenser, evaporator, expansion valve / orifice tube, accumulator or receiver-drier, blower motor, blend and mode doors / motors, blower motor(s), heater control valves, and heater core. Aluminum, steel and rubber hoses and lines connect all these components together.  This system was designed as a closed system and should not need servicing unless a problem develops, which often, can be due to corrosion.  Before 1995, R12 refrigerant was used as the refrigerant (most common brand name was “Freon” and the name “Freon” is still widely used today; however, a very inaccurate reference).  It was determined then that R12 was depleting the ozone layer and was upgraded to HFC134a refrigerant which is what is used today. A new refrigerant is also on the horizon and will be commonplace by the end of this decade in new vehicle production only. Due to new environmental legislation, each shop must be certified to purchase refrigerant and repair your vehicle.  Most people don't realize that the air conditioning system is important in cold wet weather as well as hot weather.  The A/C system removes moisture from the air every time the defroster is turned on and works in conjunction with the HVAC system. This prevents moisture from forming on the inside of the windows.  So think twice before deciding you can live without A/C.