For 1990-2009 cars

Important: Before performing any work on the air conditioning (A/C) system, refer to Handling Refrigerant R-134a . Review the following procedures before performing any work on the air conditioning system:

• | Discharging

• | Recovery

• | Recycling

The A/C system delivers dehumidified air that is heated or cooled for the occupant's comfort. The A/C system provides the following features:

• | Ram air

• | Power ventilation

• | Windshield defrosting

• | Side window defogging

Fresh outside air is drawn into the ventilation ducts by the blower during most operating conditions. Forward movement of the vehicle forces additional outside air (ram air) into the vehicle.

The air is pushed by the blower motor through the ventilation ducts in the following path:

1. Through the evaporator
2. Through the heater core
3. Into the passenger compartment

The refrigeration system chills the evaporator to almost freezing for the A/C or the defrosting operating modes. As the air passes through the evaporator, the air temperature drops. The decreased air temperature causes moisture in the air to condense on the evaporator core fins. The moisture leaves the vehicle by a gravity feed through a drain hole, dehumidifying the vehicle.

From the evaporator case some or all of the air may pass through the heater core. The engine coolant warms the heater core. Any ambient air which is not to be heated bypasses the heater core and then mixes with the heated air before entering the passenger compartment.

Set the fresh/recirculating control lever to recirculation in order to obtain the maximum A/C level. Most of the air entering the blower during this mode is taken from the passenger compartment (recirculated) where the air is likely to be cooler than the outside air.

For the heater-only or the ventilation modes, the A/C system can be shut off. When the A/C system is shut off, no cooling is provided. The operator can turn off the A/C system by setting the A/C switch to the OFF position. The proportions of the air directed through or around the heater core governs the amount of heating, in the same manner as with A/C. The heater control unit assembly in the instrument panel gives the operator a means of selecting the following operations when the engine is running:

• | The operating mode

• | The air temperature

• | The blower speed