Nissan Maxima Service and Repair Manual: System description
- Compressor control function
- Automatic air conditioner system
- Mode door control system
- Air mix door control system
- Intake door control system
- Blower motor control system
- Magnet clutch control system
- Can communication system
- Diagnosis system (HVAC)
Description PRINCIPLE OF OPERATION A/C compressor is not activated. Functional circuit diagram CAN (1): A/C switch signal : Blower fan motor switch signal CAN (2): A/C compressor request signal RX: A/C switch signal : Fan ON signal : Defroster signal Functional initial inspection chart Fail-Safe FAIL-SAFE FUNCTION If a communication error exists between the A/C auto amp.
System Diagram CONTROL SYSTEM The control system consists of input sensors, switches, the A/C auto amp. (microcomputer) and outputs. The relationship of these components is as shown in the figure below: System Description CONTROL OPERATION Display The operation status of the HVAC system is displayed on the screen. A/C Switch Assembly Temperature control switch (driver side) A/C ON/OFF switch Rear window defogger switch OFF switch/fan control dial Fresh air switch DUAL mode switch Temperature control switch (passenger side) Mode switch Recirculation switch Defroster switch AUTO switch MODE SWITCH The air discharge outlets are controlled with this switch.
System Diagram 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 The A/C auto amp. receives data from each of the sensors. 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. 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.
System Diagram System Description 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. SYSTEM OPERATION The A/C auto amp. receives data from each of the sensors. 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. 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.
System Diagram System Description 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. SYSTEM OPERATION 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.
System Diagram System Description 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 System Operation For airflow, the manual selection (1-7) with the fan control dial has priority. 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.
System Diagram System Description The A/C auto amp. controls A/C compressor operation by ambient temperature, intake air temperature and signal from ECM. SYSTEM OPERATION 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.
System Description 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.
CONSULT Function CONSULT can display each diagnosis item using the diagnosis test modes as shown. CONSULT application items SELF-DIAGNOSTIC RESULT Display Item List *: Perform self-diagnosis under sunshine. When performing indoors, aim a light (more than 60 W) at sunload sensor, otherwise self-diagnosis reports an error even though the sunload sensor is functioning normally. DATA MONITOR Display item list ACTIVE TEST HVAC TEST NOTE: Perform the inspection of each output device after starting the engine, because the A/C compressor has been operating.
