If the freon charge is good, and the compressor WILL engage and stay on, but the dash vents still blow warm air from all vents, then the air delivery system needs to be checked next.

Depending on the vehicle, there are several doors, actuators and motors that direct the incoming air over the A/C evaporator to cool the air. Any number of problems can cause the air to either be warm, or just a little cool.

Air Temperature Door

This door is the main door that directs airflow over the A/C evaporator core, or the heater core. A problem with the door or the actuator that controls it will cause temperature problems.

Vent Mode
When the driver selects the VENT mode, air is delivered through the instrument panel outlets and a small amount is delivered to the floor. Vacuum or voltage is applied to the mode actuator through the vacuum line or electrical harness- depending on the system, and to the defrost actuator. The mode actuator will retract, opening the Vent Door. The defroster actuator will retract, closing the Defroster Door and open the Heater Door through mechanical linkage.

Bi-Level Mode
When the driver selects the BI-LEVEL mode, cool air is delivered through the instrument panel outlets while warm air is delivered through the floor outlets. Vacuum or voltage is applied to the mode actuator, and to the defrost actuator. Applying vacuum or voltage to both sides of the mode actuator will hold the Vent Door stationary in the half open position. The defroster actuator will retract, closing the Defroster Door and open the Heater Door through mechanical linkage.

Floor Mode
When the driver selects the FLOOR mode, air is delivered through the floor outlets with some toward the windshield and side vents. Vacuum or voltage is applied to the mode actuator, and to the defrost actuator. The mode actuator will retract, closing the Vent Door. The defroster actuator will retract, closing the Defroster Door and open the Heater Door through mechanical linkage.

Defog Mode
When the driver selects the defog mode, air delivery is divided between the floor and windshield outlets. Vacuum or voltage is applied to the mode actuator, and to the defrost actuator. The mode actuator will retract, closing the Vent Door. Applying vacuum or voltage to both sides of the defroster actuator will hold the Defroster Door stationary in the half open position. The Heater Door will also be held stationary in the half open position through mechanical linkage.

FRONT DEFROST

When selected, the A/C compressor is activated and outside air is brought into the vehicle. Air will be directed toward the windshield with a small amount of air toward the side window outlets. Vacuum or voltage is applied to the mode actuator and to the defrost actuator. The mode actuator will retract, closing the Vent Door. The defroster actuator will retract, opening the Defroster Door and close the Heater Door through mechanical linkage. Recirculation mode is not available in front defrost. The rear window defogger does not affect the HVAC system at all.