Nissan Quest E52. Manual - part 724

HAC-26

< SYSTEM DESCRIPTION >

[AUTOMATIC AIR CONDITIONING]

SYSTEM

REAR AUTOMATIC AIR CONDITIONING SYSTEM : System Description

INFOID:0000000009652518

SYSTEM DIAGRAM

DESCRIPTION

• Rear automatic air conditioning system is controlled by each function of A/C auto amp.
• Each operation of rear automatic air conditioning system can be controlled by front A/C control (built-in A/C

auto amp.) and rear A/C control.

CONTROL BY A/C AUTO AMP.

•

HAC-27, "REAR AUTOMATIC AIR CONDITIONING SYSTEM : Temperature Control"

•

HAC-27, "REAR AUTOMATIC AIR CONDITIONING SYSTEM : Air Outlet Control"

•

HAC-27, "REAR AUTOMATIC AIR CONDITIONING SYSTEM : Air Flow Control"

•

HAC-19, "FRONT AUTOMATIC AIR CONDITIONING SYSTEM : Air Inlet Control"

•

HAC-29, "REAR AUTOMATIC AIR CONDITIONING SYSTEM : Door Control"

• Correction for input value

Ambient temperature correction

- A/C auto amp. inputs the temperature detected by ambient sensor as the ambient temperature. 
- A/C auto amp. performs the correction of the temperature detected by ambient sensor for rear air condition-

ing control. 

- A/C auto amp. selects and uses the initial value of ambient temperature data depending on the engine cool-

ant temperature when turning the ignition switch from OFF to ON. The detection temperature of the ambient
sensor is used when engine coolant temperature is low [less than approximately 56

°

C (133

°

F)]. The mem-

ory data (before the ignition switch is OFF) when the engine is warmed up [approximately 56

°

C (133

°

F) or

more]. 

- The correction of the ambient temperature is not performed when the detection temperature of the ambient

temperature is less than approximately 

−

20

°

C (–4

°

F). 

Rear in-vehicle temperature correction

- A/C auto amp. inputs the temperature detected by rear in-vehicle sensor as the rear in-vehicle temperature. 
- A/C auto amp. performs the correction of the temperature detected by rear in-vehicle sensor for rear air con-

ditioning control. 

- A/C auto amp. performs the correction so that the recognition passenger room temperature (rear side)

changes depending on the difference between the detected passenger room temperature (rear side) and the
recognition passenger room temperature (rear side). If the difference is large, the changing is early. The
changing becomes slow as the difference becomes small. 

Intake temperature correction

- A/C auto amp. inputs the temperature detected by intake sensor as the intake temperature (front evaporator

temperature). 

- A/C auto amp. performs the correction of the temperature detected by intake sensor for rear air conditioning

control. 

JMIIA1772GB

SYSTEM

HAC-27

< SYSTEM DESCRIPTION >

[AUTOMATIC AIR CONDITIONING]

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- A/C auto amp. performs the correction so that the recognition intake temperature changes depending on the

difference between the detected intake temperature and the recognition intake temperature. If the difference
is large, the changing is early. The changing becomes slow as the difference becomes small. 
NOTE:
A/C auto amp. calculates rear evaporator temperature according to front evaporator temperature (intake
sensor detection temperature).

Sunload amount correction

- A/C auto amp. inputs the sunload amount detected by sunload sensor. 
- A/C auto amp. performs the correction of the sunload amount detected by sunload sensor for rear air condi-

tioning control. 

- When the sunload amount suddenly changes, for example when entering a tunnel, perform the correction so

that the recognition sunload amount of the A/C auto amp. changes slowly. 

Set temperature correction

- A/C auto amp. performs the correction to the target temperature set by the temperature control switch so as

to match the temperature felt by the passengers depending on the ambient temperature detected by ambi-
ent sensor and controls it so that the in-vehicle temperature is always the most suitable. 

REAR AUTOMATIC AIR CONDITIONING SYSTEM : Temperature Control

INFOID:0000000009652519

• When ignition switch is in the ON position, A/C auto amp. always

automatically controls temperature regardless of rear air condition-
ing operational state.

• A/C auto amp. calculates the target rear air mix door opening

angle depending on set temperature, rear in-vehicle temperature,
ambient temperature, and sunload. 

• Rear air mix door is controlled depending on the comparison of

current rear air mix door opening angle and target rear air mix door
opening angle.

• Regardless of rear in-vehicle temperature, ambient temperature,

and sunload, rear air mix door is fixed at the fully cold position
when set temperature is 18

°

C (60

°

F), and at the fully hot position

when set temperature is 32

°

C (90

°

F).

REAR AUTOMATIC AIR CONDITIONING SYSTEM : Air Outlet Control

INFOID:0000000009652520

While air outlet is in automatic control, A/C auto amp. selects the
rear mode door position depending on a target rear air mix door
opening angle and outlet air temperature calculated from sunload.

REAR AUTOMATIC AIR CONDITIONING SYSTEM : Air Flow Control

INFOID:0000000009652521

DESCRIPTION

• A/C auto amp. changes duty ratio of rear blower motor control signal to control air flow continuously. When

air flow is increased, duty ratio of rear blower motor control signal gradually increases to prevent a sudden
increase in air flow.

• In addition to manual control and automatic control, air flow control is compose of starting air flow control,

low coolant temperature starting control, high in-vehicle temperature starting control, and fan speed control
at door motor operation.

AUTOMATIC AIR FLOW CONTROL

• A/C auto amp. decides target air flow depending on target air mix door opening angle.

JMIIA0734GB

JMIIA0733GB

HAC-28

< SYSTEM DESCRIPTION >

[AUTOMATIC AIR CONDITIONING]

SYSTEM

• A/C auto amp. changes duty ratio of rear blower motor control signal to control air flow continuously so that

air flow matches to target air flow.

• When air outlet is VENT or B/L, the minimum air flow is changed

depending on sunload.

STARTING AIR FLOW CONTROL

When rear blower motor is activated, A/C auto amp. gradually
increases duty ratio of blower fan control signal to prevent a sudden
increase in discharge air flow. It takes approximately 8 seconds for
air flow to reach HI from LOW.

LOW COOLANT TEMPERATURE STARTING CONTROL

If the engine coolant temperature is 56

°

C (133

°

F) or less, to prevent

a cold discharged air flow, A/C auto amp. suspends rear blower
motor activation for the maximum 150 seconds depending on target
air mix door opening angle. After this, blower fan control signal is
increased gradually, and rear blower motor is activated.

HIGH IN-VEHICLE TEMPERATURE STARTING CONTROL

When evaporator temperature is high [intake air temperature sensor value is 35

°

C (95

°

F) or more], to prevent

a hot discharged air flow, A/C auto amp. suspends rear blower motor activation for approximately 3 seconds
so that evaporator is cooled by refrigerant.

FAN SPEED CONTROL AT DOOR MOTOR OPERATION

When rear mode door motor is activated while air flow is more than the specified value, A/C auto amp.
reduces temporarily fan speed so that rear mode door moves smoothly.

JMIIA0738GB

JMIIA0739GB

JMIIA0740GB

SYSTEM

HAC-29

< SYSTEM DESCRIPTION >

[AUTOMATIC AIR CONDITIONING]

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REAR AUTOMATIC AIR CONDITIONING SYSTEM : Door Control

INFOID:0000000009652522

DOOR MOTOR CONTROL

• LCU (Local Control Unit) is built into each door motor. And detects door position by PBR (Potentio Balance

Resistor). 

• A/C auto amp. communicates with each LCU via communication line. And receives each door position feed-

back signal from each LCU.

• Each LCU controls each door to the appropriate position depending on the control signal from A/C auto amp. 
• Each LCU transmits the signal of door movement completion to A/C auto amp., when the door movement is

completed.

SWITCHES AND THEIR CONTROL FUNCTION

JMIIA1776GB

1.

Rear blower motor

2.

Rear evaporator

3.

Rear air mix door

4.

Rear heater core

5.

Rear mode door

Recirculation air

Discharge air

Rear ventilator

Rear foot

JMIIA1008ZZ