FRONT AUTOMATIC AIR CONDITIONING SYSTEM : Compressor Control

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

DESCRIPTION

When the compressor activation condition is satisfied while front blower motor is activated, A/C auto amp. transmits A/C ON signal and blower fan ON signal to BCM.
BCM transmits the A/C ON signal and blower fan ON signal to ECM via CAN communication line. Refer to "SIGNAL BUFFER SYSTEM : SYSTEM DESCRIPTION ".
ECM judges the conditions of each sensor (refrigerant pressure sensor signal, accelerator position signal, etc.), and transmits the A/C compressor request signal to IPDM E/R via CAN communication line.
By receiving the A/C compressor request signal from ECM, IPDM E/R turns the A/C relay to ON, and activates the compressor. Refer to "RELAY CONTROL SYSTEM : SYSTEM DESCRIPTION ".

CONTROL BY A/C AUTO AMP.

Low Temperature Protection Control

When intake sensor detects that front evaporator fin temperature is 2.5°C (37°F) or less, A/C auto amp. requests ECM to turn the compressor OFF, and stops the compressor.

When the front evaporator fin temperature returns to 4.0°C (39°F) or more, the compressor is activated.

Fig 1: Front Automatic Air Conditioning System Compressor Control Graph

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

CONTROL BY ECM

Compressor Protection Control at Pressure Malfunction

When the high-pressure side value that is detected by refrigerant pressure sensor is as per the following state, ECM requests IPDM E/R to turn A/C relay OFF and stops the compressor.

3.12 MPa (31.8 kg/cm² , 452 psi) or more (When the engine speed is less than 1,500 RPM)
2.74 MPa (27.9 kg/cm² , 397 psi) or more (When the engine speed is 1,500 RPM or more)
0.14 MPa (1.4 kg/cm² , 20 psi) or less

Compressor Oil Circulation Control

When the engine starts while the engine coolant temperature is 56°C (133°F) or less, ECM activates the compressor for approximately 6 seconds and circulates the compressor oil once.

Air Conditioning Cut Control

When the engine condition is high load, ECM transmit A/C relay OFF request to IPDM E/R, and stops the compressor. Refer to "AIR CONDITIONING CUT CONTROL : SYSTEM DESCRIPTION ".