The A/C system is much more complex than just adding freon when the system no longer produces cold air. The system became low on freon because of a leak. If freon leaks out, air can get into the system. 3% air in the system is the maximum limit. Every vehicle has a specification for the amount of freon that the system requires. An overcharge or undercharge can cause poor A/C performance. Pressure readings are used to determine problems in the system. There are low and high side pressure readings. By analyzing the pressure readings from both sides, a Technician can evaluate possible problems with the system. Adding dye will help locate the leaks. Once the system is leak-free and properly charged, it should give you good service for some time.

There are several filters on an automobile. Many cars today have a cabin filter that filters the outside air before it enters the heater box. This filter needs to be replaced every 10 to 15,000 miles. Driving conditions such as dusty roads may require more frequent filter replacement. The cabin air filter is designed to filter the outside air that enters the automobile’s cabin. The outside air enters through vents, usually at the base of the front windshield. The air conditioning component shown above is the evaporator of an older vehicle. This older vehicle was not equipped with a cabin air filter.

As you can see, debris has been collected in this unit, restricting the transfer of cold air to the cabin. This debris could include bird feathers, weeds, dust, dirt, molds, and more. The smell of the air passing through this unit may not be pleasant. The heater control unit on the dash allows you to recycle the air in the cabin. You close a door that shuts off the outside air by pushing the recycle button to the on position.

The blow motor circulates the heating and air conditioning air through the vents, defrost, and floor settings. The operator controls the motor’s speeds by switching the fan speeds on the dash unit. As the different speeds are requested, a resistor changes the fan blower motor’s voltage.