The valve allows fresh (outside) air to enter the HVAC module when the air inlet valve is open. The air inlet valve forces recirculation of the air in the passenger compartment when the air inlet valve closes. The air inlet valve is located on the top of the HVAC module at the right front corner of the passenger compartment.

The blower moves the air in the following manner:

The evaporator dehumidifies the air. The resulting moisture expels through a drain at the front of the dash. The position of the blower speed switch controls the blower speed. A resistor in the electrical circuit dictates the blower speed. Refer to HVAC Blower Controls Circuit Description in Heating Ventilation and Air Conditioning for complete wiring information for the A/C electrical system.

In all of the A/C modes, the heater core heats the cool dehumidified air in order to achieve the desired passenger compartment temperature. The movement of the temperature control knob actuates the temperature valve. The control knob determines how much heat the incoming air adds. The heater valve directs the heated air according to the mode setting. The following components are located in the middle of the HVAC module, downstream of the evaporator:

The mode valve determines the direction of the air mix according to the input from the mode switch. The mode valve is vacuum actuated. The mode valve is located in the top of the HVAC module.

The defrost valve directs the air mix to the windshield based on the input from the mode switch. The defrost valve is vacuum actuated. The defrost valve is located in the top of the HVAC module near the front of the dash.

A system of ducts and outlets directs the air from the HVAC module to the passenger compartment. In cases of a poor air output, inspect the following components for obstructions or other objects:

The objects above may have fallen into the following places:

The vehicle has a flow-through ventilation system. A supply of outside air flows into the vehicle when the blower motor is running. When the side windows are closed, some air will flow to the following areas:

The compressor is equipped with a pressure relief valve. The pressure relief valve (2) is placed in the system as a safety factor. Under certain conditions, the refrigerant on the discharge side may exceed the designed operating pressure. In order to prevent system damage, engineers designed the valve in order to open automatically when the high side pressure exceeds a specified amount. Correct the following conditions that may cause the valve to open:

Replace the following items as needed:

The cooling fan operation ensures proper operation of the A/C system. The coolant fan ensures that the proper amount of air flows across the condenser throughout the vehicle's operating range.

Inspect the fan operation during the A/C diagnosis procedure. Give special attention to the fan when the following conditions occur:

The cooling fan control circuits vary according to the following conditions:

For electrical information, refer to Engine Controls.