Nissan Sentra Service Manual: System description

COMPONENT PARTS

Component Part Location

1. ECM
2. IPDM E/R
3. BCM (view with combination meter removed)
4. A/C auto amp. (view with A/C switch assembly removed)
5. A/C switch assembly
6. A/C Compressor
7. Refrigerant pressure sensor (view with front bumper fascia removed)
8. Fuse Block (J/B), Front blower motor relay
9. Blower motor (view with front A/C assembly removed from vehicle)
10. Mode door motor
11. Intake door motor
12. Air mix door motor
13. Intake sensor
14. Variable blower control

Component Description

Component	Description
A/C auto amp.	A/C auto amp. controls front automatic air conditioning system by inputting and calculating signals from each sensor and each switch.
A/C Compressor	Vaporized refrigerant is drawn into the A/C compressor from the evaporator, where it is compressed to a high pressure, high temperature vapor. The hot, compressed vapor is then discharged to the condenser.
A/C switch assembly	The A/C switch assembly controls the operation of the A/C and heating system based on inputs from the temperature control knob, the mode switches, the blower control dial, the ambient temperature sensor, the intake sensor, and inputs received from the ECM across the CAN. Diagnosis of the A/C switch assembly can be performed using the CONSULT. There is no self-diagnostic feature available.
Air mix door motor	The air mix door controls the mix of hot or cold air that enters the ventilation system. It is controlled by the A/C auto amp. based on the position of the temperature dial. The air mix door motor LH receives position commands from the A/C auto amp.
BCM	The BCM receives the fan ON and A/C ON signals from the A/C auto amp. and sends a compressor ON request to the ECM.
Blower motor	The blower motor varies the speed at which the air flows through the ventilation system.
ECM	The ECM sends a compressor ON request to the IPDM E/R based on the status of engine operation and load as well as refrigerant pressure information. If all the conditions are met for A/C operation, the ECM transmits the compressor ON request to the IPDM E/R.
Blower motor relay	The blower motor relay controls the flow of current to fuse 20, 21 and 22 in the Fuse Block (J/B). The relay is connected directly to ground, and is energized when the ignition switch is in the ON or START position.
Fuse Block (J/B)	Located in the passenger compartment, behind the left lower IP, the Fuse Block (J/B) contains the front blower motor relay and several fuses required for the air conditioner control system.
Intake door motor	The intake door motor controls the position of the intake door. Fresh air is allowed to enter the cabin in one position, and recirculated inside air is allowed to enter in the other position. The intake door motor receives position commands from the A/C auto amp.
Intake sensor	The intake sensor measures the temperature of the front evaporator fins. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.
IPDM E/R	Refer to PCS-7, "RELAY CONTROL SYSTEM : System Description" (with Intelligent Key system) or PCS-35, "RELAY CONTROL SYSTEM : System Description" (without Intelligent Key system).
Mode door motor	The mode door controls the direction the conditioned air passes through the ventilation system. Through a series of levers and gears, the mode door controls the defrost door, the foot door, and the vent door. There are 5 preset positions: VENT, B/L, FOOT, D/F, and DEF. The mode door motor receives position commands from the A/C auto amp.
Refrigerant pressure sensor	Refer to EC-29, "Refrigerant Pressure Sensor".

SYSTEM

System Diagram

System Description

• The manual air conditioning system is controlled by a sequence of functions from the front air control, BCM, ECM, and IPDM E/R.

Controlled by front air control:

• HAC-122, "Air Flow Control"
• HAC-122, "Air Inlet Control"
• HAC-122, "Air Outlet Control"
• HAC-122, "Compressor Control"
• HAC-123, "Door Control"
• HAC-126, "Temperature Control"

Controlled by BCM:

• Air conditioning request signal.

  Refer to BCS-8, "BODY CONTROL SYSTEM : System Description" (with Intelligent Key system) or BCS-79, "BODY CONTROL SYSTEM : System Description" (without Intelligent Key system).

Control by ECM

• Cooling fan control Refer to EC-47, "COOLING FAN CONTROL : System Description".
• Air conditioning cut control Refer to EC-46, "AIR CONDITIONING CUT CONTROL : System Description".

Control by IPDM E/R

• Relay control.

  Refer to PCS-7, "RELAY CONTROL SYSTEM : System Description" (with Intelligent Key system) or PCS- 35, "RELAY CONTROL SYSTEM : System Description" (without Intelligent Key system).

• Cooling fan control.

  Refer to EC-47, "COOLING FAN CONTROL : System Description".

Air Flow Control

DESCRIPTION

• Front air control changes duty ratio of front blower motor control signal to control air flow continuously. When air flow is increased, duty ratio of front blower motor control signal gradually increases to prevent a sudden increase in air flow.
• In addition to manual control, air flow control is composed of fan speed control at door motor operation.

FAN SPEED CONTROL AT DOOR MOTOR OPERATION

When mode door motor is activated while air flow is more than the specified value, front air control temporarily reduces fan speed so that mode door moves smoothly.

Air Inlet Control

The intake door position is automatically controlled in MAX A/C and DEF modes. The intake door is controlled by customer input in the other modes.

Air Outlet Control

Air outlet control is controlled by customer input. When the A/C is turned off by turning the blower control dial fully counterclockwise, the front air control retains the current selections and returns to these selections the next time the blower control dial is turned to any fan position.

NOTE:

If ambient temperature is excessively low, D/F is selected to prevent windshield fogging when air outlet is set to FOOT.

Compressor Control

DESCRIPTION

In order for the IPDM E/R to complete a compressor ON request, the following conditions must be met:

1. The BCM detects a Fan ON signal from the front air control. The front air control grounds the fan ON signal monitored by the BCM when the blower speed dial is in any of the fan speed positions.
2. The BCM detects an A/C ON signal from the front air control. The front air control grounds the A/C ON signal monitored by the BCM when:

• The A/C switch is pressed. The A/C switch LED illuminates and the front air control grounds the A/C ON signal monitored by the BCM. Any mode control button except D/F may be selected.
• The A/C switch is OFF, and the MAX A/C button is pressed. The A/C switch LED will automatically illuminate and the front air control grounds the A/C ON signal monitored by the BCM.
• The A/C switch is OFF, and the mode button for either D/F or DEF is selected. The front air control grounds the A/C ON signal monitored by the BCM, but it does not illuminate the A/C switch LED

NOTE:

If the compressor was engaged by pressing the D/F or DEF mode buttons, and the time spent in either mode exceeds 1 minute, then the compressor stays requested, even when modes other than D/F or DEF are selected, until either:

1. The ignition switch is turned OFF.
2. The blower speed dial is turned completely counterclockwise to the OFF position
3. The A/C switch is manually turned OFF.

In other words, the compressor ON request cannot be turned off in D/F or DEF modes.

REFRIGERANT PRESSURE PROTECTION

The refrigerant system is protected against excessively high- or low-pressures by the refrigerant pressure sensor, located on the liquid tank on the condenser. The refrigerant pressure sensor detects the pressure inside the refrigerant line and sends a voltage signal to the ECM. If the system pressure rises above or falls below the following values, the ECM requests the IPDM E/R to de-energize the A/C relay and disengage the compressor.

• 3.12 MPa (31.82 kg/cm2, 452.4 psi) or more (When the engine speed is less than 1,500 rpm)
• 2.74 MPa (27.95 kg/cm2, 397.3 psi) or more (When the engine speed is 1,500 rpm or more)
• 0.14 MPa (1.43 kg/cm2, 20.3 psi) or less

PRESSURE RELIEF VALVE

The refrigerant system is also protected by a pressure relief valve, located in the rear head of the compressor.

When the pressure of refrigerant in the system increases to an abnormal level [more than 2,990 kPa (30.5 kg/ cm2, 433.6 psi)], the release port on the pressure relief valve automatically opens and releases refrigerant into the atmosphere.

COMPRESSOR OIL CIRCULATION CONTROL

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

LOW TEMPERATURE PROTECTION CONTROL

• When the intake sensor detects that the front evaporator fin temperature is 1.5В°C (35В°F) or less, the front air control requests the BCM to turn the compressor OFF, and stops the compressor.
• When the front evaporator fin temperature returns to 5.0В°C (41В°F) or more, the compressor is activated.

OPERATING RATE CONTROL

When the set temperature is other than fully cold or the air outlet is “VENT”, “B/L” or “FOOT”, the front air control controls the compressor activation depending on ambient temperature.

Door Control

AIR MIX DOOR MOTOR

DESCRIPTION

• The step motor system is adopted for air mix door motor.
• When a drive signal is input from A/C auto amp. to door motor, a step motor built into the door motor rotates according to the drive signal, and then stops at the target door position
• Rotation of motor is transmitted to air mix door (upper air mix door and lower air mix door) by link, rod and lever, then air flow temperature is switched.

DRIVE METHOD

• The 4 drive coils are excited in sequence in order to drive the motor.
• Direction of rotation is changeable by recomposing pattern of excitation.

Mode door motor

DESCRIPTION

• The step motor system is adopted for mode door motor.
• When a drive signal is input from A/C auto amp. to door motor, a step motor built into the door motor rotates according to the drive signal, and then stops at the target door position.
• Rotation of motor is transmitted to mode door (center ventilator and defroster door, sub defroster door, side ventilator door, and foot door) by link, rod, and lever, then air outlet is switched.

DRIVE METHOD

• The 4 drive coils are excited in sequence in order to drive the motor.
• Direction of rotation is changeable by recomposing pattern of excitation.

INTAKE DOOR MOTOR

• Motor operates intake door according to control signal from A/C auto amp.
• Rotation of motor is transmitted to intake door by lever, then air inlet is switched.

Switches and their control function

1. Intake door
2. Blower motor
3. Air conditioner filter
4. Evaporator
5. Upper air mix door (driver side/passenger side)
6. Lower air mix door (driver side/passenger side)
7. Heater core
8. Foot door
9. Side ventilator door
10. Sub defroster door
11. Center ventilator and defroster door

Fresh air intake

Recirculation air

Discharge air

Defroster

Center ventilator

Side ventilator

Rear ventilator

Front foot

Rear foot

Air distribution

Temperature Control

• When the ignition switch is in the on position, the customer uses the front air control temperature control dial to set the desired temperature.
• The front air control calculates the target front air mix door opening angle depending on the selected temperature, intake temperature sensor, engine coolant temperature and rpm, and ambient temperature.
• Front air mix door is controlled depending on the comparison of current front air mix door opening angle and target front air mix door opening angle.
• Regardless of ambient temperature, the front air mix door is fixed at the fully cold position when the temperature control dial is set at the full cold position and fixed at the fully hot position when the temperature control dial is set at the full hot position.

OPERATION

Switch Name and Function

A/C switch assembly

1. A/C switch
2. Blower control dial (with OFF switch)
3. DEF switch
4. Rear DEF switch
5. REC switch
6. Temperature control dial
7. MAX A/C switch
8. D/F switch
9. FOOT switch
10. B/L switch
11. VENT switch

Switch Operation

DIAGNOSIS SYSTEM (BCM) (WITH INTELLIGENT KEY SYSTEM)

COMMON ITEM

COMMON ITEM : CONSULT Function (BCM - COMMON ITEM)

Application item

CONSULT performs the following functions via CAN communication with BCM.

System application

BCM can perform the following functions.

AIR CONDITIONER

AIR CONDITIONER : CONSULT Function (BCM - AIR CONDITIONER)

Data monitor

DIAGNOSIS SYSTEM (BCM) (WITHOUT INTELLIGENT KEY SYSTEM)

COMMON ITEM

COMMON ITEM : CONSULT Function (BCM - COMMON ITEM)

Application item

CONSULT performs the following functions via CAN communication with BCM.

System application

BCM can perform the following functions.

Air conditioner

AIR CONDITIONER : CONSULT Function (BCM - AIR CONDITIONER)

DIAGNOSIS SYSTEM (IPDM E/R) (WITH INTELLIGENT KEY SYSTEM)

Diagnosis Description

Auto active test

Description

In auto active test, the IPDM E/R sends a drive signal to the following systems to check their operation.

• Front wiper (LO, HI)
• Parking lamp
• License plate lamp
• Tail lamp
• Front fog lamp (if equipped)
• Headlamp (LO, HI)
• A/C compressor (magnet clutch)
• Cooling fan

Operation Procedure

NOTE:

Never perform auto active test in the following conditions.

• Passenger door is open
• CONSULT is connected

1. Close the hood and lift the wiper arms from the windshield. (Prevent windshield damage due to wiper operation)

NOTE:

When auto active test is performed with hood opened, sprinkle water on windshield beforehand.

2. Turn the ignition switch OFF.
3. Turn the ignition switch ON, and within 20 seconds, press the driver door switch 10 times. Then turn the ignition switch OFF.
4. Turn the ignition switch ON within 10 seconds. After that the horn sounds once and the auto active test starts.
5. After a series of the following operations is repeated 3 times, auto active test is completed.

NOTE:

• When auto active test has to be cancelled halfway through test, turn the ignition switch OFF.
• When auto active test is not activated, door switch may be the cause. Check door switch. Refer to DLK-103, "Component Inspection".

Inspection in Auto Active Test

When auto active test is actuated, the following operation sequence is repeated 3 times.

Concept of Auto Active Test

• IPDM E/R starts the auto active test with the door switch signals transmitted by BCM via CAN communication.

  Therefore, the CAN communication line between IPDM E/R and BCM is considered normal if the auto active test starts successfully.

• The auto active test facilitates troubleshooting if any systems controlled by IPDM E/R cannot be operated.

Diagnosis Chart in Auto Active Test

Consult Function (IPDM E/R)

Application item

Consult performs the following functions via can communication with ipdm e/r.

Ecu identification

The IPDM E/R part number is displayed.

SELF DIAGNOSTIC RESULT

Refer to PCS-20, "DTC Index".

DATA MONITOR

ACTIVE TEST

CAN DIAG SUPPORT MNTR

Refer to LAN-13, "CAN Diagnostic Support Monitor".

DIAGNOSIS SYSTEM (IPDM E/R) (WITHOUT INTELLIGENT KEY SYSTEM)

Diagnosis Description

AUTO ACTIVE TEST

Description

In auto active test, the IPDM E/R sends a drive signal to the following systems to check their operation.

• Front wiper (LO, HI)
• Parking lamp
• License plate lamp
• Tail lamp
• Front fog lamp (if equipped)
• Headlamp (LO, HI)
• A/C compressor (magnet clutch) (if equipped)
• Cooling fan

Operation Procedure

NOTE:

Never perform auto active test in the following conditions.

• Passenger door is open
• CONSULT is connected

1. Close the hood and lift the wiper arms from the windshield. (Prevent windshield damage due to wiper operation)

NOTE:

When auto active test is performed with hood opened, sprinkle water on windshield beforehand.

2. Turn the ignition switch OFF.
3. Turn the ignition switch ON, and within 20 seconds, press the driver door switch 10 times. Then turn the ignition switch OFF.
4. Turn the ignition switch ON within 10 seconds. After that the horn sounds once and the auto active test starts.
5. After a series of the following operations is repeated 3 times, auto active test is completed.

NOTE:

• When auto active test has to be cancelled halfway through test, turn the ignition switch OFF.
• When auto active test is not activated, door switch may be the cause. Check door switch. Refer to DLK-255, "Component Inspection".

Inspection in Auto Active Test

When auto active test is actuated, the following operation sequence is repeated 3 times.

Concept of Auto Active Test

• IPDM E/R starts the auto active test with the door switch signals transmitted by BCM via CAN communication.

  Therefore, the CAN communication line between IPDM E/R and BCM is considered normal if the auto active test starts successfully.

• The auto active test facilitates troubleshooting if any systems controlled by IPDM E/R cannot be operated.

Diagnosis Chart in Auto Active Test

Consult Function (IPDM E/R)

APPLICATION ITEM

CONSULT performs the following functions via CAN communication with IPDM E/R.

Ecu identification

The IPDM E/R part number is displayed.

SELF DIAGNOSTIC RESULT

Refer to PCS-48, "DTC Index".

DATA MONITOR

ACTIVE TEST

CAN DIAG SUPPORT MNTR

Refer to LAN-13, "CAN Diagnostic Support Monitor".