Air Flow Control

WARNING: This page is about a different car, the 2011 Nissan 370Z. However, it is still accessible from the selected car via links, so may be relevant.

Description

A/C auto amp. changes duty ratio of blower motor drive signal and controls air flow continuously. When air flow is increased, duty ratio of blower motor drive 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 fan speed control, low coolant temperature starting control, high in-vehicle temperature starting control, blower speed control at door motor operation, and fan speed control at voice recognition.

Automatic Air Flow Control

A/C auto amp. decides target air flow depending on target air mix door opening angle.
A/C auto amp. changes duty ratio of blower motor drive signal and controls 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.

Fig 1: Automatic Air Flow Control Reference Graph
Courtesy of NISSAN MOTOR CO., U.S.A.

Starting Fan Speed Control

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

Fig 2: Starting Fan Speed Control Graph

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

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 blower motor activation for the maximum 150 seconds depending on target air mix door opening angle. After this, blower fan drive signal is increased gradually, and blower motor is activated.

Fig 3: Low Coolant Temperature Starting Control Reference Graph

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

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 blower motor activation for approximately 3 seconds so that evaporator is cooled by refrigerant.

Fan speed Control at Door Motor Operation

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

Fan speed Control at Voice Recognition

When the voice control (voice command) switch is operated during air flow automatic control, A/C auto amp. decreases the air flow of the blower motor once and controls the air flow so as not to disturb the voice recognition function. This control continues while voice recognition function is operating.