System Construction

WARNING: This page is about a different car, the 2009 Nissan Maxima. However, it is still accessible from the selected car via links, so may be relevant.

A small network exists between the A/C auto amp., the mode door motor, the air mix door motors and the intake door motor. The A/C auto 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 A/C auto amp. and each door motor.

The following functions are contained in LCUs built into the mode door motor, the air mix door motors and the intake door motor.

Address
Motor opening angle signals
Data transmission
Motor stop and drive decision
Opening angle sensor (PBR function)
Comparison
Decision (A/C auto amp. indicated value and motor opening angle comparison)

Fig 1: A/C Auto amp Line Diagram

Courtesy of NISSAN MOTOR CO., U.S.A.

Operation

The A/C auto amp. receives data from each of the sensors. The A/C auto amp. sends mode door, the air mix door and the intake door opening angle data to the mode door motor LCU, the air mix door motor LCUs and the intake door motor LCU.

The mode door motor, the air mix door motors 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 is compared by the LCUs in each door motor with the existing decision and opening angles. Next, HOT/COLD, DEF/VENT or FRE/REC operation is selected. The new selection data is returned to the A/C auto amp.

Fig 2: A/C Auto amp Line Diagram

Courtesy of NISSAN MOTOR CO., U.S.A.

TRANSMISSION DATA AND TRANSMISSION ORDER

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

START:

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

ADDRESS:

Data sent from the A/C auto amp. is selected according to data-based decisions made by the mode door motor, the air mix door motors and the 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 has no error, door control begins.
If an error exists, the received data is rejected and the corrected data is 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 is then compiled. The error check prevents corrupted data from being used by the mode door motor, the air mix door motors 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 A/C auto amp. This completes one data transmission and control cycle.

Fig 3: Data Transmission And Control Cycle Chart

Courtesy of NISSAN MOTOR CO., U.S.A.

AIR MIX DOOR CONTROL (AUTOMATIC TEMPERATURE 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

Fan speed is automatically controlled by the temperature setting, ambient temperature, in-vehicle temperature, 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 flowing.

INTAKE DOOR CONTROL

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.

MODE DOOR CONTROL

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