For 1990-2009 cars

## Operating Modes C68

With the automatic (C68) system, the driver may manually select 8 modes of operation from the heater and A/C control. The heater and A/C programmer may also access 3 additional purge modes when certain conditions exist.

### Off

When the driver selects the OFF mode, the blower motor will run at the motor's minimum calibrated speed. The A/C compressor will be OFF.

The heater and A/C programmer will allow all vacuum actuators to vent. The valves are positioned as follows:

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

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

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

When the vehicle is moving, air flowing over the vehicle increases the air pressure just ahead of the windshield. This forces some of the air through the following path:

• | Into the outside air inlet

• | Through the heater and A/C module assembly

• | Out of the floor and the windshield outlets

The temperature control circuitry is still activated, so the heater and A/C programmer operates the air mix valve. The programmer attempts to match the inside temperature set by the occupant of the vehicle. Because the compressor is not running, the system air may be warmed, but the air cannot be cooled.

### Auto

When the driver selects the AUTO mode, the programmer will turn on the AUTO temperature indicators. The blower indicators turn off, indicating AUTO control. The driver may override AUTO blower control in the following manner:

• | For Oldsmobile, turn the fan speed knob.

• | For Buick and Pontiac, press the fan speed rocker.

The heater and A/C programmer evaluates the information that is supplied the following components:

• | The heater and A/C control

• | A network of sensors

• | A/C

• | BI-LEVEL

• | DEFOG

• | HEAT

The programmer energizes the appropriate solenoids in order to enter this mode.

Information that is supplied to the programmer determines if one of the following actions is performed:

• | Outside air is drawn into the system (NORM A/C mode)

• | Inside air is recirculated (MAX A/C mode)

The heater and A/C programmer determines the proper air discharge temperatures. The programmer engages the air mix valve actuators in order to move the air mix valves to the proper position.

### Floor/Windshield (Defog)

When the driver selects the DEFOG mode, the blower motor turns ON. The driver may manually adjust the blower speed. If the outside temperature is above 8°C (48°F), the following actions occur:

• | The A/C LED illuminates.

• | The compressor activates.

The compressor runs in order to maintain the evaporator core at about 1°C (33°F).

The heater and A/C programmer allows all of the vacuum actuators to vent the same as in the OFF mode:

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

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

• | The defrost-A/C valve is in the defrost 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 heater and A/C programmer energizes the air mix actuators in order to perform the following functions:

1. Determine the proper air mix air discharge temperatures
2. Position the valves accordingly

### Mid/Floor (Bi-Level)

When the driver selects the BI-LEVEL mode, the blower motor turns ON. The driver may manually adjust the blower speed.

The vacuum actuators move to the following positions:

• | The heater and A/C programmer supplies vacuum to the defrost-A/C valve.

• | The outside air-recirculation valve vents in the outside air position.

• | The defrost-A/C valve vents in the A/C position.

• | The heater-A/C bi-level valve vents 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 and the floor outlets.

The heater and A/C programmer energizes the air mix actuators in order to do the following:

1. Determine the proper air discharge temperatures
2. Position the air mix valves accordingly

### Recirc (Recirculate)

When the driver selects the RECIRC function, the programmer allows vacuum to be supplied to the O/S air recirculation valve actuator. This positions the O/S air recirculation valve in the recirculate position.

The RECIRC function is available for operation in the following modes:

• | UPPER

• | LOWER

• | BI-LEVEL

The RECIRC function is not allowed in the following modes, because usage may cause windshield fogging:

• | DEFOG

• | FROST DEFROST

The RECIRC function operates for approximately 10 minutes before the function shuts itself off. The driver may additionally reactivate the RECIRC function. While the RECIRC function is operational, any manual mode changes or ignition cycles will cancel the function. This will allow outside air into the system.

### Front Defrost

When the driver selects the FRONT DEFROST mode, the blower motor turns ON. The driver may manually adjust the blower speed. If the outside temperature is above 8°C (48°F), the following actions occur:

• | The A/C LED illuminates.

• | The compressor activates.

The compressor runs in order to maintain the evaporator core at about 1°C (33°F).

The vacuum actuators move to the following positions:

• | The heater and A/C programmer supplies vacuum to one side of the heater-A/C bi-level valve.

• | The air-inlet valve vents in the outside air position.

• | The defrost-A/C valve vents in the defrost position.

• | The heater-A/C bi-level valve vents in the A/C position.

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

The heater and A/C programmer performs the following functions:

1. Determines the proper air discharge temperatures
2. Positions the air mix valves accordingly

### Mid (Upper)

When the driver selects the UPPER mode, the blower motor turns ON. The driver may manually adjust the blower speed by turning the fan speed knob.

The vacuum actuators move to the following positions:

• | The heater and A/C programmer supplies vacuum to the defrost-A/C valve.

• | The heater and A/C programmer supplies vacuum to one side of the heater-A/C bi-level valve.

• | The air-inlet valve vents in the outside air position.

• | The defrost-A/C valve vents in the A/C position.

• | The heater-A/C bi-level valve vents 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 heater and A/C programmer energizes the air mix actuators in order to perform the following functions:

1. Determine the proper air discharge temperatures
2. Position the air mix valves accordingly

### Floor (Lower)

When the driver selects the LOWER mode, the blower motor turns ON. The driver may manually adjust the blower. The driver may activate the A/C compressor by pressing the A/C button. If the outside temperature is above 7.2°-10°C (45°-50°F), the A/C runs in order to maintain the evaporator core at about 1°C (33°F).

The vacuum actuators move to the following positions:

• | The heater and A/C programmer supplies vacuum to one side of the heater-A/C-bi-level valve.

• | The air-inlet valve vents in the outside air position.

• | The defrost-A/C valve vents in the defrost position.

• | The heater-A/C-bi-level valve vents in the heater position.

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

The heater and A/C programmer energizes the air mix actuators in order to perform the following functions:

1. Determine the proper air discharge temperatures
2. Position the air mix valves accordingly

## Operating Modes CJ2

The dual zone (CJ2) has 9 modes available. The heater and A/C programmer may also access 3 additional purge modes when certain conditions exist.

### Off

When the driver selects the OFF mode, the blower motor will operate at the motor's minimum calibrated speed. The A/C compressor will turn OFF.

The heater and A/C programmer will allow all of the vacuum actuators to vent. The valves are positioned in the following manner:

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

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

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

When the vehicle is moving, air flowing over the vehicle increases the air pressure just ahead of the windshield. This forces some of the air through the following path:

• | Into the outside air inlet

• | Through the heater and A/C module assembly

• | Out of the floor outlet and the windshield outlets

The temperature control circuitry is still activated, so the heater and A/C programmer operates the air mix valve. The programmer attempts to match the inside temperature set by the occupant of the vehicle. Because the compressor is not running, the system air may be warmed, but the air cannot be cooled.

### Auto

When the driver selects the AUTO mode, the programmer will turn on the AUTO temperature indicators. The blower indicators turn off, indicating AUTO control. The driver may override the AUTO blower control in the following manner:

• | For Oldsmobile, turn the fan speed knob.

• | For Buick and Pontiac, press the fan speed rocker.

The heater and A/C programmer evaluates the information that is supplied by the following components:

• | The heater and A/C control

• | A network of sensors

The programmer determines which of the following modes is required:

• | A/C

• | BI-LEVEL

• | DEFOG

• | HEAT

The programmer energizes the appropriate solenoids in order to enter this mode.

Information that is supplied to the programmer also determines if one of the following actions occur:

• | Outside air is drawn into the system (NORM A/C mode)

• | Inside air is recirculated (MAX A/C mode)

The heater and A/C programmer determines the proper air discharge temperatures. The programmer powers the air mix valve actuators in order to move the air mix valves to the proper position.

### Defog (Oldsmobile) or Floor/Windshield (Buick)

When the driver selects the DEFOG mode, the blower motor turns ON. The driver may manually adjust the blower speed by turning the fan speed knob. If the outside temperature is above 8°C (48°F), the following actions occur:

• | The A/C LED illuminates.

• | The compressor activates.

The compressor runs in order to maintain the evaporator core at about 1°C (33°F).

The heater and A/C programmer allows all of the vacuum actuators to vent the same as in the OFF mode:

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

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

• | The defrost-A/C valve is in the defrost 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 heater and A/C programmer energizes the air mix actuator in order to perform the following functions:

1. Determine the proper air discharge temperatures
2. Position the air mix valves accordingly

### Bi-Level (Oldsmobile) or Mid/Floor (Buick)

When the driver selects the BI-LEVEL mode, the blower motor turns ON. The driver may manually adjust the blower speed.

The vacuum actuators move to the following positions:

• | The heater and A/C programmer applies vacuum to the defrost-A/C valve.

• | The outside air-recirculation valve vents in the outside air position.

• | The defrost-A/C valve vents in the A/C position.

• | The heater-A/C-bi-level valve vents in the bi-level position.

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

The heater and A/C programmer energizes the air mix actuators in order to perform the following functions:

1. Determine the proper air discharge temperatures
2. Position the air mix valves accordingly

### Recirc (Recirculate)

When the driver selects the RECIRC function, the programmer allows vacuum to be supplied to the O/S air recirculation valve actuator. This positions the O/S air recirculation valve in the recirculate position.

The RECIRC function is available for operation in the following modes:

• | UPPER

• | LOWER

• | BI-LEVEL

The RECIRC function is not allowed in the following modes, because usage may cause windshield fogging:

• | DEFOG

• | FROST DEFROST

The RECIRC function operates for approximately 10 minutes before the function shuts itself off. The driver may additionally reactivate the RECIRC function. While the RECIRC function is operational, any manual mode changes or ignition cycles will cancel the function. This will allow outside air into the system.

### Front Defrost

When the driver selects the FRONT DEFROST mode, the blower motor turns ON. The driver may manually adjust the blower speed. If the outside temperature is above 8°C (48°F), the following actions occur:

• | The A/C LED illuminates.

• | The compressor activates.

The compressor runs in order to maintain the evaporator core at about 1°C (33°F).

The vacuum actuators move to the following positions:

• | The heater and A/C programmer supplies vacuum to one side of the heater-A/C-bi-level valve.

• | The air-inlet valve vents in the outside air position.

• | The defrost-A/C valve vents in the defrost position.

• | The heater-A/C-bi-level valve vents in the A/C position.

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

The heater and A/C programmer air mix actuator energizes in order to perform the following functions:

1. Determine the proper air discharge temperatures
2. Position the air mix valves accordingly

### Upper (Oldsmobile) or Mid (Buick)

When the driver selects the UPPER mode, the blower motor turns ON. The driver may manually adjust the blower speed.

The vacuum actuators move to the following positions:

• | The heater and A/C programmer supplies vacuum to the defrost-A/C valve.

• | The heater and A/C programmer supplies vacuum to one side of the heater-A/C-bi-level valve.

• | The air-inlet valve vents in the outside air position.

• | The defrost-A/C valve vents in the A/C position.

• | The heater-A/C-bi-level valve vents in the A/C position.

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

The heater and A/C programmer energizes the air mix actuator in order to perform the following functions:

1. Determine the proper air discharge temperatures
2. Position the air mix valves accordingly

### Lower (Oldsmobile) or Floor (Buick)

When the driver selects the LOWER mode, the blower motor turns ON. The driver may manually adjust the blower speed. The driver may activate the A/C compressor by pressing the A/C button. If the outside temperature is above 7.2°-10°C (45°-50°F), the A/C operates in order to maintain the evaporator core at about 1°C (33°F).

The vacuum actuators move to the following positions:

• | The heater and A/C programmer applies vacuum to one side of the heater-A/C bi-level valve.

• | The air-inlet valve vents in the outside air position.

• | The defrost-A/C valve vents in the defrost position.

• | The heater-A/C-bi-level valve vents in the heater position.

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

The heater and A/C programmer energizes the air mix actuator in order to perform the following functions:

1. Determine the proper air discharge temperatures
2. Position the air mix valves accordingly

### Dual Zone

You many select the DUAL ZONE mode in 1 of the following 2 ways:

• | Press the PASS button

• | Adjust the passenger control head

The programmer independently operates the driver and passenger air mix valves. The passenger may operate the passenger temperature in order to request a warmer or a cooler temperature on the passenger side of the vehicle. When this occurs, the programmer energizes the passenger air mix valve actuator in order to increase or decrease the passenger side discharge temperature.