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 10A (circuit 241) in the fuse block.

The RADIO fuse 10A (circuit 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 circuit 241 from battery voltage to approximately 1.5 volts.

The heater-A/C control provides a ground from G200 through circuit 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 in the RUN position through circuit 241 from the HVAC/DRL fuse in the fuse block. The actuator receives ground from G200 through circuit 150.

The heater-A/C control sends a signal through circuit 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 circuit 241 from the HVAC/DRL fuse in the fuse block. It also receives ground from G200 through circuit 150. The heater-A/C control sends a signal through circuit 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 25A (circuit 641) in the fuse block to the auxiliary heater A/C control. The temperature control potentiometer varies the voltage in circuit 641 from battery voltage to approximately 1.5 volts.

The auxiliary heater-A/C control provides a ground path from G401 through circuit 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 circuit 641 from the RR HVAC fuse 25A in the fuse block. The actuator receives ground from G401 through circuit 850.

The auxiliary heater-A/C control sends a signal through circuit 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.

### Auxiliary Coolant Bypass Pump

The auxiliary coolant bypass pump provides supplemental coolant flow in cold ambient temperatures to the heater core. The auxiliary coolant bypass pump power is supplied by ckt61 from the auxiliary coolant bypass pump switch. The ground is provide by the ground circuit (circuit 1050). The auxiliary coolant bypass pump switch provides power to the auxiliary coolant bypass pump control circuit (circuit 61) at temperatures between 2°C (36°F) and 8°C (47°F). The auxiliary coolant bypass pump switch is supplied voltage from the ignition 1 voltage circuit (circuit 1239).