Heater & Air Conditioning Control System (Automatic): Overview Nissan Maxima A35

DESCRIPTION

The purpose of the operational check is to check that the individual system operates normally.

Conditions : Engine running at normal operating temperature

PRINCIPLE OF OPERATION

Compressor is not activated.

Functional circuit diagram

Scheme 61

Functional initial inspection chart

COMPRESSOR FUNCTIONAL INITIAL INSPECTION CHART

CONTROL OPERATION

Display

The operation status of the HVAC system is displayed on the screen.

Scheme 62

A/C and AV Switch Assembly

Scheme 63

MODE SWITCH

The air discharge outlets are controlled with this switch.

TEMPERATURE CONTROL DIAL (Driver Side)

The set temperature is increased or decreased with this dial.

TEMPERATURE CONTROL DIAL (Passenger Side)

1. The set temperature is increased or decreased with this dial.
2. When the temperature control dial is turned, DUAL switch indicator is turned ON.

AUTO SWITCH

1. The compressor, intake doors, air mix doors, mode doors and blower speed are automatically controlled so that the in-vehicle temperature will reach, and be maintained at the set temperature selected by the operator.
2. When pressing the AUTO switch, air inlet, air outlet, fan speed, and discharge air temperature are automatically controlled.

DEFROSTER SWITCH

Mode doors are set to the defrost position with this switch. Also, intake doors are set to the outside air position, and compressor turns ON.

A/C SWITCH

Compressor turns ON or OFF with this switch.

(Pressing the A/C switch when the A/C switch is ON turns OFF the A/C switch and compressor.)

FAN CONTROL DIAL

The fan speed is manually controlled with this dial. Seven speeds are available for manual control (as shown on the display screen).

ON - OFF SWITCH

Compressor and blower turn OFF, intake doors and the mode doors are automatically controlled.

REAR WINDOW DEFOGGER SWITCH

When indicator is ON, rear window is defogged.

RECIRCULATION SWITCH

1. When the REC switch is ON, the REC switch indicator is turned ON, and air inlet is set to REC.

FRESH AIR SWITCH

1. When the FRE switch is ON, the FRE switch indicator is turned ON, and air inlet is set to FRE.

DUAL MODE SWITCH

1. When the DUAL switch indicator is ON, the driver side and passenger side, temperature can each be set independently.
2. When the DUAL switch indicator is OFF, the driver side outlet and setting temperature are applied to both sides.

System Description

The mode door is automatically controlled by the temperature setting, ambient temperature, in-vehicle temperature, intake temperature and amount of sunload.

SYSTEM OPERATION

1. The A/C auto amp. receives data from each of the sensors.
2. The A/C auto amp. sends the air mix door, the mode door and the intake door opening angle data to the air mix door motor LCU(s), the mode door motor LCU and the intake door motor LCU.
3. The air mix door motor(s), the mode door motor and the intake door motor read their respective signals according to the address signal. Opening angle indication signals received from the A/C auto amp. and each of the motor position sensors, are compared by the LCUs in each door motor with the existing decision and opening angles.
4. Next, HOT/COLD, DEF/VENT or FRE/REC operation is selected. The newly selected data is returned to the A/C auto amp.

Scheme 64

Mode Door Control Specification

Mode position can be selected manually by pressing the MODE switch or the DEF switch on the A/C and AV switch assembly. Pressing the AUTO switch allows automatic control by the A/C auto amp. During the automatic control of a mode position, a mode door position (VENT, B/L, FOOT, or D/F) is selected based on a target air mix door opening angle and sunload sensor, calculated by the A/C auto amp. In addition, the D/F is selected to prevent windshield fogging only when ambient temperature is extremely low.

Scheme 65

Scheme 66

The air mix doors are automatically controlled so that in-vehicle temperature is maintained at a predetermined value by the temperature setting, ambient temperature, intake temperature and amount of sunload.

1. The A/C auto amp. receives data from each of the sensors.
2. The A/C auto amp. sends air mix door, the mode door and the intake door opening angle data to the air mix door motor LCU(s), the mode door motor LCU and the intake door motor LCU.
3. The air mix door motor(s), the mode door motor and the intake door motor read their respective signals according to the address signal. Opening angle indication signals received from the A/C auto amp. and each of the motor position sensors are compared by the LCUs in each door motor with the existing decision and opening angles.
4. Next, HOT/COLD, DEF/VENT or FRE/REC operation is selected. The newly selected data is returned to the A/C auto amp.

Door Motor Circuit

Scheme 67

Air Mix Door Control Specification

When ignition switch is ON, the A/C auto amp. continuously and automatically controls temperatures, regardless of air conditioner operational condition. When setting a target temperature with the temperature control switch, the A/C auto amp. corrects the set temperature and decides a target air mix door opening angle. The A/C auto amp. controls the air mix door according, to the target air mix door opening angle and the current air mix door opening angle, keeping an optimum air mix door opening angle. When the temperature is set at 18°C (60°F), air mix door is set on full-cold, and when the temperature is set at 32°C (90°F), it is set to full-hot.

Scheme 68

Scheme 69

The intake doors are automatically controlled by the temperature setting, ambient temperature, in-vehicle temperature, intake temperature, amount of sunload and ON/OFF operation of the compressor.

The intake door control judges intake door position based on the ambient temperature, the intake air temperature and the in-vehicle temperature. When in shifting mode position D/F, if the DEF or OFF switches are pressed, or when the A/C switch is OFF, the A/C auto amp. sets the intake door to the FRE position.

Scheme 70

Scheme 71

Scheme 72

Fan speed is automatically controlled by the temperature setting, ambient temperature, in-vehicle temperature, intake temperature, amount of sunload and air mix door position.

By pressing the AUTO switch, the blower motor starts to gradually increase airflow volume.

When engine coolant temperature is low, the blower motor operation is delayed to prevent cool air from flowing.

System Operation

Scheme 73

1. For airflow, the manual selection (1-7) with the fan control dial has priority.
2. If the AUTO switch is pressed or if the DEF switch is pressed while in the OFF condition, it changes to the automatic control by A/C auto amp.
3. When increasing the airflow, it changes the duty ratio of the blower motor drive signal to prevent the airflow from suddenly increasing.
4. There are the following types of airflow control: starting airflow control, starting airflow control at low coolant temperature, starting airflow control at high in-vehicle temperature, and airflow control at actuator operation in addition to manual control, normal automatic airflow control.

Normal Automatic Airflow Control

1. When the target temperature is set by the temperature control dial of A/C and AV switch assembly, the A/C auto amp. performs the calculation and decides the target according to the signal from each sensor.
2. The A/C auto amp. changes the duty ratio of blower motor drive signal and controls the airflow, continuously, so that the airflow becomes the target airflow.
3. The minimum airflow will change according to the sunload when the air discharge outlet is VENT or B/L.

Scheme 74

Starting Airflow Control

1. When starting the automatic control of airflow, the system gradually increases the duty ratio of the blower motor drive signal to prevent too much air from blowing.
2. The time period from when the airflow changes from LO to HI is approximately 8 seconds.
3. It becomes the starting airflow control at low coolant temperature according to the calculation result of the A/C auto amp. and engine coolant temperature [approximately 56°C (133°F) or less] during the automatic airflow control.
4. Do not perform the starting airflow control when the air discharge outlet is set to DEF.

Starting Fan Speed Control

Start-up from COLD SOAK Condition (Automatic mode)

In cold start-up condition where the engine coolant temperature is below 56°C (133°F), the blower does not operate for a short period of time (up to 150 seconds). The exact start delay time varies depending on the ambient temperature and engine coolant temperature.

In the most extreme case (very low ambient temperature) the blower start delay is 150 seconds, as described above. After this delay, the blower will operate at low speed until the engine coolant temperature rises above 56°C (133°F), and then the fan speed increases to the objective speed.

Start-up from usual or HOT SOAK Condition (Automatic mode)

The blower will begin operation momentarily after the AUTO switch is pressed. The fan speed rises gradually to the objective speed over a time period of 3 seconds or less (actual time depends on the objective fan speed).

Scheme 75

The A/C auto amp. controls compressor operation by ambient temperature, intake air temperature and signal from ECM.

When the A/C switch, the AUTO switch, or the DEF switch is pressed, or when shifting mode position to D/F, the A/C auto amp. transmits the A/C switch signal and blower fan motor switch signal to the ECM, via CAN communication.

ECM judges whether compressor can be turned ON, based on each sensor status (refrigerant-pressure sensor signal, throttle angle, etc.). If the ECM judges that the compressor can be turned ON, it sends A/C compressor request signal to the IPDM E/R, via CAN communication.

Upon receipt of A/C compressor request signal from the ECM, the IPDM E/R turns the A/C relay ON to operate the compressor.

When sending A/C compressor request signal to the IPDM E/R via CAN communication line, the ECM simultaneously sends A/C compressor feedback signal to A/C auto amp. via CAN communication line. The ECM sends A/C compressor feedback signal to A/C auto amp., then, uses input A/C compressor feedback signal to control air inlet.

Compressor Protection Control

The ECM makes the A/C relay turn OFF and stops the compressor when pressure on the high-pressure side, detected by the refrigerant pressure sensor, is over approximately 3,119 kPa (31.8 kg/cm 2 , 452 psi), or below approximately 118 kPa (1.2 kg/cm 2 , 17 psi).

Low Temperature Protection Control

Turn the A/C relay to OFF and stop the A/C compressor by the signal from the A/C auto amp., according to the evaporator passing air temperature detected by the intake sensor and the ambient temperature detected by the ambient sensor.

CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. Many electronic control units are equipped onto each vehicle, and each control unit shares information and links with other control units during operation (not independent). In CAN communication, control units are connected with 2 communication lines (CAN-H line, CAN-L line) allowing a high rate of information transmission with less wiring. Each control unit transmits/receives data but selectively reads required data only. For details, refer to " CAN SYSTEM SPECIFICATION CHART ".

CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. Many electronic control units are equipped onto a vehicle, and each control unit shares information and links with other control units during operation (not independent). In CAN communication, control units are connected with two communication lines (CAN-H line, CAN-L line) allowing a high rate of information transmission with less wiring. Each control unit transmits/receives data but selectively reads required data only.

CAN Communication Signal Chart. Refer to " HOW TO USE CAN COMMUNICATION SIGNAL CHART ".

Initial diagnosis of A/C auto amp.

COMPONENT DESCRIPTION

Ambient Sensor

1. The ambient sensor (1) is installed to the front bumper reinforcement.
2. It detects ambient temperature and converts it into a resistance value which is then input into the A/C auto amp.

Scheme 76

Ambient Sensor Circuit

Scheme 77

In-vehicle Sensor

1. The in-vehicle sensor (1) is located on instrument lower cover (LH).
2. It converts variations in compartment air temperature drawn from the aspirator into a resistance value. It is then input into the A/C auto amp.

Scheme 78

In-vehicle Sensor Circuit

Scheme 79

Aspirator

The aspirator (1) is located on driver side of heater & cooling unit assembly. It produces vacuum pressure due to air discharged from the heater & cooling unit assembly, continuously taking compartment air in the aspirator.

Scheme 80

Scheme 81

Intake Sensor

1. The intake sensor is located on the evaporator.
2. It converts air temperature after it passes through the evaporator into a resistance value which is then input to the A/C auto amp.

Scheme 82

Intake Sensor Circuit

Scheme 83

Sunload Sensor

1. The sunload sensor (1) is located on the driver side defroster grille.
2. It detects sunload entering through windshield by means of a photo diode. The sensor converts the sunload into a current value, which is then input into the A/C auto amp.

Scheme 84

Sunload Sensor Circuit

Scheme 85

Air Mix Door Motor (Driver side)

1. The air mix door motor (driver side) (1) is attached to the heater & cooling unit assembly.
2. It rotates so that the air mix door is opened or closed to a position set by the A/C auto amp.
3. Motor rotation is then conveyed through a shaft and the air mix door position feedback is then sent to the A/C auto amp. by PBR built-in air mix door motor.

Scheme 86

Air Mix Door Motor (Passenger Side)

1. The air mix door motor (passenger side) (1) is attached to the heater & cooling unit assembly.
2. It rotates so that the air mix door is opened or closed to a position set by the A/C auto amp.
3. Motor rotation is then conveyed through a shaft and the air mix door position feedback is then sent to the A/C auto amp. by PBR built-in air mix door motor.

Scheme 87

Mode Door Motor

1. The mode door motor (1) is attached to the heater & cooling unit assembly.
2. It rotates so that air is discharged from the outlet set by the A/C auto amp. Motor rotation is conveyed to a link which activates the mode door.

Scheme 88

Intake Door Motor

1. The intake door motor (1) is attached to the blower unit.
2. It rotates so that air is drawn from inlets set by the A/C auto amp. Motor rotation is conveyed to a lever which activates the intake door.

Scheme 89

Brush-less Motor

The blower motor utilizes a brush-less motor with a rotating magnet. Quietness is improved over previous motors where the brush was the point of contact and the coil rotated.

Scheme 90

Scheme 91

A/C auto amp. controls A/C compressor operation by ambient temperature and signal from ECM.

Low Temperature Protection Control

A/C auto amp. will turn the A/C compressor ON or OFF as determined by a signal detected by ambient sensor.

When ambient temperature is greater than 4°C (39°F), the A/C compressor turns ON. The A/C compressor turns OFF when ambient temperature is less than 2.5°C (37°F).

Scheme 92

A/C AUTO AMP. : Description

COMPONENT DESCRIPTION

A/C Auto Amp. (Air Conditioner Automatic Amplifier)

The A/C auto amp. (1) has a built-in microcomputer that processes information sent from various sensors needed for air conditioner operation. The air mix door motor(s), the mode door motor, the intake door motor, the blower motor and the compressor are then controlled.

When the various switches and temperature control dial are operated, data is input to the A/C auto amp. from the AV control unit using CAN communication.

The A/C auto amp. is operated with control mechanisms. Signals from various switches and Potentio Temperature Control (PTC) are directly entered into the A/C auto amp.

Scheme 93

Power Supply and Ground Circuit for A/C Auto Amp.

Scheme 94

IDENTIFICATION

Vehicles with factory installed fluorescent dye have a green label.

IDENTIFICATION LABEL FOR VEHICLE

Vehicles with factory installed fluorescent dye have this identification label on the underside of hood.

The purpose of the operational check is to check that the individual system operates normally.

Conditions : Engine running at normal operating temperature

A/C compressor is not activated.

Functional circuit diagram

Scheme 95

Functional initial inspection chart

COMPRESSOR CONTROL FUNCTIONAL INITIAL INSPECTION CHART

Display

The operation status of the HVAC system is displayed on the screen.

Scheme 96

A/C Switch Assembly

Scheme 97

MODE SWITCH

The air discharge outlets are controlled with this switch.

TEMPERATURE CONTROL SWITCH (Driver Side)

The set temperature is increased or decreased with this switch.

TEMPERATURE CONTROL SWITCH (Passenger Side)

1. The set temperature is increased or decreased with this switch.
2. When the temperature control switch is pressed, DUAL mode indicator is turned ON.

AUTO SWITCH

1. The A/C compressor, intake doors, air mix doors, mode doors and blower speed are automatically controlled so that the in-vehicle temperature will reach, and be maintained at the set temperature selected by the operator.
2. When pressing the AUTO switch, air inlet, air outlet, fan speed, and discharge air temperature are automatically controlled.

DEFROSTER SWITCH

Mode doors are set to the defrost position with this switch. Also, intake doors are set to the outside air position, and A/C compressor turns ON.

A/C SWITCH

A/C compressor turns ON or OFF with this switch.

(Pressing the A/C switch, when the A/C switch is ON, turns OFF the A/C switch and A/C compressor.)

FAN CONTROL DIAL

The fan speed is manually controlled with this dial. Seven speeds are available for manual control (as shown on the display screen).

OFF SWITCH

A/C compressor and blower turn OFF, intake doors and the mode doors are automatically controlled.

REAR WINDOW DEFOGGER SWITCH

When indicator is ON, rear window is defogged.

RECIRCULATION SWITCH

1. When the REC switch is ON, the REC switch indicator is turned ON, and air inlet is set to REC.

FRESH AIR SWITCH

1. When the FRE switch is ON, the FRE switch indicator is turned ON, and air inlet is set to FRE.

DUAL MODE SWITCH

1. When the DUAL switch indicator is ON, the driver side and passenger side temperature can each be set independently.
2. When the DUAL switch indicator is OFF, the driver side outlet and setting temperature are applied to both sides.

The mode door is automatically controlled by the temperature setting, ambient temperature, in-vehicle temperature, intake temperature and amount of sunload.

1. The A/C auto amp. receives data from each of the sensors.
2. The A/C auto amp. sends the air mix door, the mode door and the intake door opening angle data to the air mix door motor LCU(s), the mode door motor LCU and the intake door motor LCU.
3. The air mix door motor(s), the mode door motor and the intake door motor read their respective signals according to the address signal. Opening angle indication signals received from the A/C auto amp. and each of the motor position sensors, are compared by the LCUs in each door motor with the existing decision and opening angles.
4. Next, HOT/COLD, DEF/VENT or FRE/REC operation is selected. The newly selected data is returned to the A/C auto amp.

Door Motor Circuit

Scheme 98

Mode Door Control Specification

Mode position can be selected manually by pressing the MODE switch or the DEF switch on the A/C switch assembly. Pressing the AUTO switch allows automatic control by the A/C auto amp. During the automatic control of a mode position, a mode door position (VENT, B/L, FOOT, or D/F) is selected based on a target air mix door opening angle and the sunload sensor, calculated by the A/C auto amp. In addition, the D/F is selected to prevent windshield fogging only when ambient temperature is extremely low.

Scheme 99

Scheme 100

The air mix doors are automatically controlled so that in-vehicle temperature is maintained at a predetermined value by the temperature setting, ambient temperature, intake temperature and amount of sunload.

1. The A/C auto amp. receives data from each of the sensors.
2. The A/C auto amp. sends air mix door, the mode door and the intake door opening angle data to the air mix door motor LCU(s), the mode door motor LCU and the intake door motor LCU.
3. The air mix door motor(s), the mode door motor and the intake door motor read their respective signals according to the address signal. Opening angle indication signals received from the A/C auto amp. and each of the motor position sensors, are compared by the LCUs in each door motor with the existing decision and opening angles.
4. Next, HOT/COLD, DEF/VENT or FRE/REC operation is selected. The newly selected data is returned to the A/C auto amp.

Scheme 101

Air Mix Door Control Specification

When ignition switch is ON, the A/C auto amp. continuously and automatically controls temperatures, regardless of air conditioner operational condition. When setting a target temperature with the temperature control switch, the A/C auto amp. corrects the set temperature and decides a target air mix door opening angle. The A/C auto amp. controls the air mix door, according to the target air mix door opening angle and the current air mix door opening angle, keeping an optimum air mix door opening angle. When the temperature is set at 18°C (60°F), air mix door is set on full-cold, and when the temperature is set at 32°C (90°F), it is set to full-hot.

Scheme 102

Scheme 103

The intake doors are automatically controlled by the temperature setting, ambient temperature, in-vehicle temperature, intake temperature, amount of sunload and ON/OFF operation of the A/C compressor.

The intake door control judges intake door position based on the ambient temperature, the intake air temperature and the in-vehicle temperature. When in shifting mode position D/F, if the DEF or OFF switches are pressed, or when the A/C switch is OFF, the A/C auto amp. sets the intake door to the FRE position.

Scheme 104

Scheme 105

Scheme 106

Fan speed is automatically controlled by the temperature setting, ambient temperature, in-vehicle temperature, intake temperature, amount of sunload and air mix door position.

By pressing the AUTO switch, the blower motor starts to gradually increase airflow volume.

When engine coolant temperature is low, the blower motor operation is delayed to prevent cool air from flowing.

System Operation

Scheme 107

1. For airflow, the manual selection (1-7) with the fan control dial has priority.
2. If the AUTO switch is pressed or if the DEF switch is pressed while in the OFF condition, it changes to the automatic control by A/C auto amp.
3. When increasing the airflow, it changes the duty ratio of the blower motor drive signal to prevent the airflow from suddenly increasing.
4. There are the following types of airflow control: starting airflow control, starting airflow control at low coolant temperature, starting airflow control at high in-vehicle temperature, and airflow control at actuator operation in addition to manual control, normal automatic airflow control.

Normal Automatic Airflow Control

1. When the target temperature is set by the temperature control switch of A/C switch assembly, the A/C auto amp. performs the calculation and decides the target according to the signal from each sensor.
2. The A/C auto amp. changes the duty ratio of blower motor drive signal and controls the airflow, continuously, so that the airflow becomes the target airflow.
3. The minimum airflow will change, according to the sunload, when the air discharge outlet is VENT or B/L.

Fan Speed Control Specification

Scheme 108

Starting Airflow Control

1. When starting the automatic control of airflow, the system gradually increases the duty ratio of the blower motor drive signal to prevent too much air from blowing.
2. The time period from when the airflow changes from LO to HI is approximately 8 seconds.
3. It becomes the starting airflow control at low coolant temperature according to the calculation result of the A/C auto amp. and engine coolant temperature [approximately 56°C (133°F) or less] during the automatic airflow control.
4. Do not perform the starting airflow control when the air discharge outlet is set to DEF.

Starting Fan Speed Control

Start-up from COLD SOAK Condition (Automatic mode)

In cold start-up condition, where the engine coolant temperature is below 56°C (133°F), the blower does not operate for a short period of time (up to 150 seconds). The exact start delay time varies depending on the ambient temperature and engine coolant temperature.

In the most extreme case (very low ambient temperature) the blower start delay is 150 seconds, as described above. After this delay, the blower will operate at low speed until the engine coolant temperature rises above 56°C (133°F), and then the fan speed increases to the objective speed.

Start-up from usual or HOT SOAK Condition (Automatic mode)

The blower will begin operation momentarily after the AUTO switch is pressed. The fan speed rises gradually to the objective speed over a time period of 3 seconds or less (actual time depends on the objective fan speed).

Scheme 109

The A/C auto amp. controls A/C compressor operation by ambient temperature, intake air temperature and signal from ECM.

When the A/C switch, the AUTO switch, or the DEF switch is pressed, or when shifting mode position to D/F, the A/C auto amp. transmits the A/C switch signal and blower fan motor switch signal to the ECM, via CAN communication.

ECM judges whether the A/C compressor can be turned ON, based on each sensor status (refrigerant-pressure sensor signal, throttle angle, etc.). If the ECM judges that the A/C compressor can be turned ON, it sends A/C compressor request signal to the IPDM E/R, via CAN communication.

Upon receipt of A/C compressor request signal from the ECM, the IPDM E/R turns the A/C relay ON to operate the A/C compressor.

When sending A/C compressor request signal to the IPDM E/R via CAN communication line, the ECM simultaneously sends A/C compressor feedback signal to A/C auto amp. via CAN communication line.

The ECM sends A/C compressor feedback signal to A/C auto amp., then, uses input A/C compressor feedback signal to control air inlet.

A/C compressor Protection Control

The ECM makes the A/C relay turn OFF and stops the A/C compressor when pressure on the high-pressure side, detected by the refrigerant pressure sensor, is over approximately 3,119 kPa (31.8 kg/cm 2 , 452 psi), or below approximately 118 kPa (1.2 kg/cm 2 , 17 psi).

Low Temperature Protection Control

Turn the A/C relay to OFF and stop the A/C compressor by the signal from the A/C auto amp., according to the evaporator passing air temperature detected by the intake sensor and the ambient temperature detected by the ambient sensor.

CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. Many electronic control units are equipped onto each vehicle, and each control unit shares information and links with other control units during operation (not independent). In CAN communication, control units are connected with 2 communication lines (CAN-H line, CAN-L line) allowing a high rate of information transmission with less wiring. Each control unit transmits/receives data but selectively reads required data only. For details, refer to " CAN SYSTEM SPECIFICATION CHART ".

CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. Many electronic control units are equipped onto a vehicle, and each control unit shares information and links with other control units during operation (not independent). In CAN communication, control units are connected with two communication lines (CAN-H line, CAN-L line) allowing a high rate of information transmission with less wiring. Each control unit transmits/receives data but selectively reads required data only.

CAN Communication Signal Chart. Refer to " HOW TO USE CAN COMMUNICATION SIGNAL CHART ".

Initial diagnosis of A/C auto amp.

Ambient Sensor

1. The ambient sensor (1) is installed to the front bumper reinforcement.
2. It detects ambient temperature and converts it into a resistance value which is then input into the A/C auto amp.

Scheme 110

Ambient Sensor Circuit

Scheme 111

In-vehicle Sensor

1. The in-vehicle sensor (1) is located on instrument lower cover (LH).
2. It converts variations in compartment air temperature drawn from the aspirator into a resistance value. It is then input into the A/C auto amp.

Scheme 112

In-vehicle Sensor Circuit

Scheme 113

Aspirator

The aspirator (1) is located on driver side of heater & cooling unit assembly. It produces vacuum pressure due to air discharged from the heater & cooling unit assembly, continuously taking compartment air in the aspirator.

Scheme 114

Scheme 115

Intake Sensor

1. The intake sensor is located on the evaporator.
2. It converts air temperature after it passes through the evaporator into a resistance value which is then input to the A/C auto amp.

Scheme 116

Intake Sensor Circuit

Scheme 117

Sunload Sensor

1. The sunload sensor (1) is located on the driver side defroster grille.
2. It detects sunload entering through windshield by means of a photo diode. The sensor converts the sunload into a current value, which is then input into the A/C auto amp.

Scheme 118

Sunload Sensor Circuit

Scheme 119

Air Mix Door Motor (driver side)

1. The air mix door motor (driver side) (1) is attached to the heater & cooling unit assembly.
2. It rotates so that the air mix door is opened or closed to a position set by the A/C auto amp.
3. Motor rotation is then conveyed through a shaft and the air mix door position feedback is then sent to the A/C auto amp. by PBR built-in air mix door motor.

Scheme 120

Air Mix Door Motor (passenger side)

1. The air mix door motor (passenger side) (1) is attached to the heater & cooling unit assembly.
2. It rotates so that the air mix door is opened or closed to a position set by the A/C auto amp.
3. Motor rotation is then conveyed through a shaft and the air mix door position feedback is then sent to the A/C auto amp. by PBR built-in air mix door motor.

Scheme 121

Mode Door Motor

1. The mode door motor (1) is attached to the heater & cooling unit assembly.
2. It rotates so that air is discharged from the outlet set by the A/C auto amp. Motor rotation is conveyed to a link which activates the mode door.

Scheme 122

Intake Door Motor

1. The intake door motor (1) is attached to the blower unit.
2. It rotates so that air is drawn from inlets set by the A/C auto amp. Motor rotation is conveyed to a lever which activates the intake door.

Scheme 123

Brush-less Motor

The blower motor utilizes a brush-less motor with a rotating magnet. Quietness is improved over previous motors where the brush was the point of contact and the coil rotated.

Scheme 124

Scheme 125

A/C auto amp. controls A/C compressor operation by ambient temperature and signal from ECM.

Low Temperature Protection Control

A/C auto amp. will turn the A/C compressor ON or OFF as determined by a signal detected by ambient sensor.

When ambient temperature is greater than 4°C (39°F), the A/C compressor turns ON. The A/C compressor turns OFF when ambient temperature is less than 2.5°C (37°F).

Scheme 126

COMPONENT DESCRIPTION

A/C Auto Amp. (Air Conditioner Automatic Amplifier)

The A/C auto amp. (1) has a built-in microcomputer that processes information sent from various sensors needed for air conditioner operation. The air mix door motor(s), the mode door motor, the intake door motor, the blower motor and the A/C compressor are then controlled.

When the various switches and temperature control switches are operated, data is input to the A/C auto amp. from the AV switch assembly using CAN communication.

The A/C auto amp. is operated with control mechanisms. Signals from various switches and Potentio Temperature Control (PTC) are directly entered into the A/C auto amp.

Scheme 127

Power Supply and Ground Circuit for A/C Auto Amp.

Scheme 128

Vehicles with factory installed fluorescent dye have a green label.

Vehicles with factory installed fluorescent dye have this identification label on the underside of hood.

See also:
• COMPONENT FUNCTION CHECK
• REMOVAL AND INSTALLATION