Infiniti FX35 / FX45. Manual - part 107

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AIR CONDITIONER CONTROL

AIR CONDITIONER CONTROL

Description of Air Conditioner LAN Control System

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The LAN (Local Area Network) system consists of unified meter and A/C amp., mode door motor, air mix door
motors and intake door motor.
A configuration of these components is shown in the figure below.

System Construction

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A small network is constructed between the unified meter and A/C amp., air mix door motors, mode door
motor and intake door motor. The unified meter and A/C amp. and motors are connected by data transmission
lines and motor power supply lines. The LAN network is built through the ground circuits of each door motor.
Addresses, motor opening angle signals, motor stop signals and error checking messages are all transmitted
through the data transmission lines connecting the unified meter and A/C amp. and each door motor.
The following functions are contained in LCUs built into the air mix door motors, the mode door motor and the
intake door motor.
• Address
• Motor opening angle signals
• Data transmission
• Motor stop and drive decision
• Opening angle sensor (PBR function)
• Comparison
• Decision (Unified meter and A/C amp. indicated value and motor opening angle comparison)

OPERATION

The unified meter and A/C amp. receives data from each of the sensors. The unified meter and A/C amp.
sends mode door, air mix door and intake door opening angle data to the mode door motor LCU, air mix door
motor LCU and intake door motor LCU.
The mode door motor, air mix door motors and intake door motor read their respective signals according to the
address signal. Opening angle indication signals received from the unified meter and A/C amp. and each of
the motor position sensors is compared by the LCUs in each door motor with the existing decision and open-
ing angles. Subsequently, HOT/COLD, DEF/VENT and FRE/REC operation is selected. The new selection
data is returned to the unified meter and A/C amp.

SJIA1609E

RJIA1747E

AIR CONDITIONER CONTROL

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TRANSMISSION DATA AND TRANSMISSION ORDER

Unified meter and A/C amp. data is transmitted consecutively to each of the door motors following the form
shown in figure below.

Start:

Initial compulsory signal is sent to each of the door motors.

Address:

Data sent from the unified meter and A/C amp. are selected according to data-based decisions made by the
air mix door motor, mode door motor and intake door motor.
If the addresses are identical, the opening angle data and error check signals are received by the door motor
LCUs. The LCUs then make the appropriate error decision. If the opening angle data have no error, door con-
trol begins.
If an error exists, the received data are rejected and corrected data received. Finally, door control is based
upon the corrected opening angle data.

Opening Angle:

Data that shows the indicated door opening angle of each door motor.

Error Check:

In this procedure, transmitted and received data is checked for errors. Error data are then compiled. The error
check prevents corrupted data from being used by the air mix door motor, the mode door motor and the intake
door motor. Error data can be related to the following symptoms.
• Malfunction of electrical frequency
• Poor electrical connections
• Signal leakage from transmission lines
• Signal level fluctuation

Stop Signal:

At the end of each transmission, a stop operation, in-operation, or internal malfunction message is delivered to
the unified meter and A/C amp. This completes one data transmission and control cycle.

AIR MIX DOOR CONTROL (AUTOMATIC TEMPERATURE CONTROL)

RJIA1748E

RJIA1749E

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AIR CONDITIONER CONTROL

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

FAN SPEED CONTROL

Blower speed is automatically controlled by the temperature setting, ambient temperature, in-vehicle tempera-
ture, intake temperature, amount of sunload and air mix door position.
With pressing AUTO switch, the blower motor starts to gradually increase air flow volume.
When engine coolant temperature is low, the blower motor operation is delayed to prevent cool air from flow-
ing.

INTAKE DOOR CONTROL

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

MODE DOOR CONTROL

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

MAGNET CLUTCH CONTROL

When A/C switch, AUTO switch or DEF switch is pressed, unified meter and A/C amp. transmits compressor
ON signal to BCM.
BCM sends compressor ON signal to ECM, via CAN communication.
ECM judges whether compressor can be turned ON, based on each sensor status (refrigerant-pressure sen-
sor signal, throttle angle, etc.). If it judges compressor can be turned ON, it sends compressor ON signal to
IPDM E/R, via CAN communication.
Upon receipt of compressor ON signal from ECM, IPDM E/R turns air conditioner relay ON to operate com-
pressor.
When sending compressor ON signal to IPDM E/R via CAN communication, ECM simultaneously sends com-
pressor feedback signal to unified meter and A/C amp. via CAN communication.
Unified meter and A/C amp., then, uses input compressor feedback signal to control air inlet.

SELF-DIAGNOSIS SYSTEM

The self-diagnosis system is built into the unified meter and A/C amp. to quickly locate the cause of malfunc-
tions.

RJIA1957E

AIR CONDITIONER CONTROL

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Description of Control System

INFOID:0000000001328169

The control system consists of input sensors, switches, the unified meter and A/C amp. (microcomputer) and
outputs. The relationship of these components is shown in the figure below:

Control Operation

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DISPLAY SCREEN

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

AUTO SWITCH 

• 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.

SJIA1658E

SJIA1567E