For 1990-2009 cars

All available operating modes for C61 and C67 are listed below. The actual operating modes on your system vary by model and may not have all of the modes listed.

### OFF

When the blower motor and A/C compressor turns OFF, the following conditions are present:

• | Vacuum is not supplied to any of the vacuum actuators.

• | The air inlet valve is in the outside air position.

• | The heater and A/C BI-LEVEL valve vacuum actuator is in the bi-level position.

• | The defrost and A/C valve vacuum actuator is in the defrost position.

When the vehicle is moving, the following actions occur:

1. The air flowing over the vehicle increases the air pressure just ahead of the windshield.
2. The HVAC module directs some of the air into the air inlet and out the defroster ducts and the floor outlets.

The temperature control circuitry still activates so that the air forced through the system is directed through the heater core and warmed, if desired.

### MAX A/C

The blower motor circuitry is turned ON. The fan speed knob adjusts the blower speed. The A/C compressor activates and runs in order to keep the evaporator core at about 1°C (33°F).

Vacuum is supplied to the following components:

• | The air inlet vacuum actuator

• | The defrost and A/C valve vacuum actuator

• | One side of the heater and A/C BI-LEVEL valve vacuum actuator

The valves are in the following positions:

• | The air inlet valve is in the recirculation position.

• | The defrost and A/C valve is in the A/C position.

• | The heater and A/C BI-LEVEL valve is in the A/C position.

The blower pulls interior air into the system. The air is heated or cooled. The air is then forced through the instrument panel outlets.

The temperature control circuitry activates so that the temperature knob can adjust the discharge air temperature.

### NORM A/C

The blower motor circuitry is turned ON. The fan speed knob adjusts the blower speed. The A/C compressor activates and runs in order to keep the evaporator core at about 1°C (33°F).

Vacuum is supplied to the following components:

• | The defrost A/C valve vacuum actuator

• | One side of the heater and A/C BI-LEVEL valve vacuum actuator

The valves are in the following positions:

• | The air inlet valve is in the outside air position.

• | The defrost and A/C valve is in the A/C position.

• | The heater and A/C BI-LEVEL valve is in the A/C position.

The blower pulls outside air into the system. The air is heated or cooled. The air is then forced through the instrument panel outlets.

The temperature control circuitry activates so that the temperature knob can adjust the discharge air temperature.

### BI-LEVEL

The blower motor circuitry is turned ON. The fan speed knob adjusts the blower speed. The A/C compressor activates and runs in order to keep the evaporator core at about 1°C (33°F).

Vacuum is supplied to the defrost and A/C valve vacuum actuator.

The valves are in the following positions:

• | The air inlet valve is in the outside air position.

• | The defrost and A/C valve is in the A/C position.

• | The heater and A/C BI-LEVEL valve is in the bi-level position.

The blower pulls outside air into the system. The air is heated or cooled. The air is then forced through the instrument panel outlets.

The temperature control circuitry activates so that the temperature knob can adjust the discharge air temperature.

### VENT

The blower motor circuitry is turned ON. The fan speed knob adjusts the blower speed. The A/C compressor activates and runs in order to keep the evaporator core at about 1°C (33°F).

Vacuum is supplied to the following components:

• | The defrost A/C valve vacuum actuator

• | One side of the heater and A/C BI-LEVEL valve vacuum actuator

The valves are in the following positions:

• | The air inlet valve is in the outside air position.

• | The defrost and A/C valve is in the A/C position.

• | The heater and A/C BI-LEVEL valve is in the A/C position.

The blower pulls outside air into the system. The air is warmed or cooled. The air is then forced out of the instrument panel outlets.

The temperature control circuitry activates so that the air flowing through the system directs through the heater core. The air is warmed, if desired.

### HEATER

The blower motor circuitry is turned ON. The fan speed knob adjusts the blower speed.

Vacuum is supplied to one side of the heater and A/C BI-LEVEL valve vacuum actuator.

The valves are in the following positions:

• | The air inlet valve is in the outside air position.

• | The defrost and A/C valve is in the defrost position.

• | The heater and A/C BI-LEVEL valve is in the heater position.

The following actions occur:

1. The blower pulls outside air into the system.
2. The air is forced out of the floor outlets.

The temperature control circuitry activates so that the air flowing through the system is directed through the heater core. The temperature knob can adjust the discharge temperature.

### DEFOG

The blower motor circuitry is turned ON. The fan speed knob adjusts the blower speed. The A/C compressor activates and runs in order to keep the evaporator core at about 1°C (33°F).

Vacuum is not supplied to any of the vacuum actuators.

The valves are in the following positions:

• | The air inlet valve is in the outside air position.

• | The defrost and A/C valve vacuum actuator is in the defrost position.

• | The heater and A/C BI-LEVEL valve vacuum actuator is in the BI-LEVEL position.

The blower pulls outside air into the system. The air is heated or cooled. The air is then forced through the windshield defroster and the floor outlets.

The temperature control circuitry activates so that the temperature knob can adjust the discharge air temperature.

### DEFROST

The blower motor circuitry is turned ON. The fan speed knob adjusts the blower speed. The A/C compressor activates and runs in order to keep the evaporator core at about 1°C (33°F).

Vacuum is supplied to the one side of the heater and A/C BI-LEVEL valve vacuum actuator.

The valves are in the following positions:

• | The air inlet valve is in the outside air position.

• | The defrost and A/C valve is in the defrost position.

• | The heater and A/C BI-LEVEL valve is in the A/C position.

The blower pulls outside air into the system. The air is heated or cooled. The air is then forced out of the windshield defroster outlets.

The temperature control circuitry activates so that the temperature knob can adjust the discharge air temperature.

### RECIRC

The air inlet valve moves to the recirculation position when the vacuum is supplied to the following components:

• | The air inlet vacuum actuator

• | The defrost and A/C valve

• | One side of the heater and A/C BI-LEVEL valve vacuum actuator

The blower pulls interior air into the system. The air is heater or cooled. The air is then forced through the instrument panel outlets.

The temperature control circuitry activates so that the temperature knob can adjust the discharge air temperature.

### UPPER

The defrost and A/C valve and the heater and A/C BI-LEVEL valve are in the A/C position when the following conditions are present:

• | Vacuum is supplied to the defrost and A/C valve vacuum actuator.

• | Vacuum is supplied to one side of the heater and A/C BI-LEVEL valve.

• | The air inlet valve is in the outside air position.

The blower pulls interior air into the system. The air is heated or cooled. The air is then forced through the instrument panel outlets.

The temperature control circuitry activates so that the temperature knob can adjust the discharge air temperature.

### LOWER

The air inlet valve is in the outside air position when the following conditions are present:

• | Vacuum is supplied only to the defrost and A/C valve actuator.

• | All of the other actuators vent.

The blower pulls outside air into the system. The air is heated or cooled. The air is then forced through the floor outlets.

The temperature control circuitry activates so that the temperature knob can adjust the discharge air temperature.