Nissan Murano. Manual - part 815

HAC-34

< SYSTEM DESCRIPTION >

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INTAKE DOOR CONTROL SYSTEM

INTAKE DOOR CONTROL SYSTEM

System Diagram

INFOID:0000000009722043

System Description

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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.

SYSTEM OPERATION

The intake door control judges intake door position based on the ambient temperature, the intake air tempera-
ture and the in-vehicle temperature. When in shifting mode position D/F, if the DEF or ON/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.

Door Motor Circuit

Intake Door Control Specification

JMIIA0493GB

JPIIA0495GB

INTAKE DOOR CONTROL SYSTEM

HAC-35

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Intake door position is basically set to the FRE when the FRE indica-
tor of the DEF switch and the intake switch turn ON, and set on the
REC when the REC indicator of intake switch turns ON.
The intake door automatic control selects the FRE, the 20%FRE, or
the REC depending on the target air mix door opening angle, based
on in-vehicle temperature, ambient temperature, and sunload.

JPIIA0634GB

HAC-36

< SYSTEM DESCRIPTION >

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BLOWER MOTOR CONTROL SYSTEM

BLOWER MOTOR CONTROL SYSTEM

System Diagram

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System Description

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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.
By pressing the 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.

SYSTEM OPERATION

System operation

• For air flow, 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. 

• When increasing the air flow, it changes the duty ratio of the blower

motor drive signal to prevent the air flow from suddenly increasing. 

• There are the following types of air flow control: starting air flow

control, starting air flow control at low coolant temperature, starting
air flow control at high in-vehicle temperature, and air flow control
at actuator operation in addition to manual control, normal auto-
matic air flow control. 

Normal automatic air flow control

• When the target temperature is set by the temperature control switch of A/C control, the A/C auto amp. per-

forms the calculation and decides the target according to the signal from each sensor. 

• The A/C auto amp. changes the duty ratio of blower motor drive signal and controls the air flow continuously

so that the air flow becomes the target air flow. 

• The minimum air flow will change according to the sunload when the air discharge outlet is VENT or B/L. 

JSIIA1540GB

JSIIA0999ZZ

BLOWER MOTOR CONTROL SYSTEM

HAC-37

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Fan Speed Control Specification

Starting air flow control

• When starting the automatic control of air flow, the system gradually increases the duty ratio of the blower

motor drive signal to prevent too much air from blowing. 

• The time period from when the air flow changes from LO to HI is approximately 8 seconds. 
• It becomes the starting air flow control at low coolant temperature according to the calculation result of the A/

C auto amp. and engine coolant temperature [approximately 58

°

C (136

°

F) or less] during the automatic air

flow control. 

• Do not perform the starting air flow 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 58

°

C (136

°

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
58

°

C (136

°

F), and then the blower 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 blower speed rises gradu-
ally to the objective speed over a time period of 3 seconds or less (actual time depends on the objective
blower speed).

JPIIA0635GB