For 1990-2009 cars

### Heater A/C Control

When the ignition switch is RUN position voltage is applied to the heater A/C control through the HVAC/DRL Fuse (CKT 241) in the fuse block.

The RADIO fuse (CKT 640) in the underhood accessory wiring junction block provides voltage to the heater A/C control at all times.

The temperature control potentiometer varies voltage in CKT 241 from battery voltage to approximately 1.5 volts.

The heater A/C control provides a ground from G200 through CKT 150.

Vacuum regulates the control of air through the system.

Various positions on the control cause the control mode valves to mix and direct cooled, heated and outside air through the air ducts.

The electric slave actuator receives voltage at all times through CKT 241 from the HVAC/DRL fuse in the fuse block. The actuator receives ground from G200 through CKT 150.

The heater A/C control sends a signal through CKT 733 to the electric slave actuator. The signal is determined by the position of the temperature control. The electric slave actuator uses this signal in order to determine the position of the temperature door.

The electric air inlet actuator receives voltage through CKT 241 from the HVAC/DRL fuse in the fuse block. It also receives ground from G200 through CKT 150. The heater A/C control sends a signal through CKT 684 to the electric air inlet actuator. The signal is determined by the position of the air recirculation switch. The electric air inlet actuator uses the signal in order to determine the position of the air inlet door. The position of the door determines whether inside air or outside air is circulated.

### Auxiliary Heater-A/C Control

When the ignition switch is in the RUN position, voltage is applied through the RR HVAC fuse (CKT 641) in the fuse block to the auxiliary heater A/C control. The temperature control potentiometer varies the voltage in CKT 641 from battery voltage to approximately 1.5 volts.

The auxiliary heater A/C control provides a ground path from G401 through CKT 850. Vacuum regulates the control of air through the system. Various positions on the control cause the mode valves to mix and direct cooled, heated and outside air through the air ducts.

The auxiliary temperature valve actuator receives voltage through CKT 641 from the RR HVAC fuse in the fuse block. The actuator receives ground from G401 through CKT 850.

The auxiliary heater A/C control sends a signal through CKT 955 to the auxiliary temperature valve actuator. The position of the temperature control determines the position of the actuator. The auxiliary temperature valve actuator uses the signal in order to determine the position of the temperature door.