Air Conditioning (A/C) System Description. Pontiac Sun Runner - 4WD (Canada) 1998

For 1990-2009 cars

Important: Review the precautions on handling Refrigerant-134a (R-134a) and the information on discharging, recovery and recycling procedures, prior to performing any work on the air conditioning system. Refer to Handling Refrigerant R-134a and Refrigerant Recovery and Recharging .

The air conditioning system delivers air that has been heated, or cooled and dehumidified, in order to provide comfort for the occupants of the vehicle. The air conditioning system provides ram air, power ventilation, windshield defrosting, and side window defogging.

During most of the air conditioning system operating conditions, the blower draws fresh outside air into the ventilation ducts. Additional air (ram air) is forced into the vehicle by the forward movement of the vehicle.

Within the ventilation ducts, the blower motor pushes the air through the evaporator, then through the heater core, and into the passenger compartment. The refrigeration system chills the evaporator to almost freezing for the air conditioning or defroster operating modes. As the air passes through the evaporator, the air temperature drops which causes the moisture in the air in order to condense on the evaporator core fins. The moisture leaves the vehicle by gravity feed, through a drain hole, dehumidifying the vehicle.

Some or all of the air may pass through the heater core, warmed by the engine coolant, from the evaporator case. Any air that is not to be heated bypasses the heater core and then mixes with the heated air, prior to entering the passenger compartment.

Set the fresh/ recirc control lever to recirculation for the maximum air conditioning. 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.

The A/C may be shut off during the heater-only mode or the ventilation mode. Turn the A/C switch to the OFF position in order to turn off the A/C. The degree of heating is determined by the proportions of the air directed through or around the heater core, in the same manner as the air conditioning system. The heater control unit assembly in the instrument panel provides the means for selecting the desired operating mode, the air temperature, and the blower speed when the engine is running.