Automatic Air Conditioner: Overview Nissan Quest III

A/C Identification Label

Vehicles with factory installed fluorescent dye have an identification label on the underside of hood.

Description

The front air control provides automatic regulation of the vehicle's interior temperature. The system is based on the driver's and passenger's selected "set temperature", regardless of the outside temperature changes. This is done by utilizing a microcomputer, also referred to as the front air control, which receives input signals from the following six sensors

1. Ambient sensor
2. In-vehicle sensor
3. Intake sensor
4. Optical sensor (providing one input for driver and one input for passenger side)
5. PBR (position balanced resistor).
6. Vehicle speed sensor (via CAN communication)

The front air control uses these signals (including the set temperature) to automatically control

1. Outlet air volume
2. Air temperature
3. Air distribution

The front air control also provides separate regulation of the vehicle's interior temperature for the rear passenger area. The system is based on the temperature and rear blower settings selected from rear control switches located on the front air control, or from the temperature and rear blower settings selected from rear control switches on the rear air control, when the front air control switches are set to the rear position.

The front air control is used to select

1. Outlet air volume
2. Air temperature/distribution

Description of Control System

The control system consists of input sensors, switches, the front air control (microcomputer) and outputs. The relationship of these components is shown in the figure below

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Control Operation

Front air control

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Rear air control

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CAN Communication System Description

Refer to CAN COMMUNICATION .

CONSULT-II BASIC OPERATION

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1. With the ignition switch OFF, connect CONSULT-II and CONSULT-II CONVERTER to the data link connector, and turn the ignition switch ON.
2. Touch "START (NISSAN BASED VHCL)".
3. Touch "HVAC" on "SELECT SYSTEM" screen. If "HVAC" is not indicated, go to «CONSULT-II DATA LINK CONNECTOR (DLC) CIRCUIT»(ref-239935-S20808400922006080400000) .

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1. Touch "SELF-DIAG RESULTS" on "SELECT DIAG MODE" screen to view all set DTC's.

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1. With the ignition switch OFF, connect CONSULT-II and CONSULT-II CONVERTER to the data link connector, and turn the ignition switch ON.
2. Touch "START (NISSAN BASED VHCL)".
3. Touch "BCM" on "SELECT SYSTEM" screen. If "BCM" is not indicated, go to «CONSULT-II DATA LINK CONNECTOR (DLC) CIRCUIT»(ref-239935-S20808400922006080400000) .

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1. Touch "AIR CONDITIONER" on "SELECT TEST ITEM" screen.
2. Touch "DATA MONITOR" on "SELECT DIAG MODE" screen.
3. Touch either "ALL SIGNALS" or "SELECTION FROM MENU" on "DATA MONITOR" screen. DATA MONITOR FUNCTION REFERENCE All signals Monitors all the items. Selection from menu Selects and monitors the individual item selected.
4. Touch "START".
5. When "SELECTION FROM MENU" is selected, touch items to be monitored. When "ALL SIGNALS" is selected, all the items will be monitored.
6. Touch "RECORD" while monitoring, then the status of the monitored item can be recorded. To stop recording, touch "STOP".

The self-diagnostic system diagnoses sensors, CAN system, battery voltage, and stuck button on front air control. Refer to applicable information (items) for details. Shifting from usual control to the self-diagnostic system is accomplished by the following

On the AV switch, hold the memory "4" button and rotate the audio "POWER/VOLUME" knob until the Self-Diagnostic screen shows on the display. Scroll down and select "Confirmation/Adjustment" with the joystick. Select "Auto Climate Control" with the joystick to start the self-test. The fan bars will flash on the display during the self-test, and then the fault codes (if any are present) will display in the ambient temperature area. Refer to " SELF-DIAGNOSIS CODE CHART ". The fault codes will continue to scroll until self-diagnostic mode is exited. To exit self-diagnostic mode, press the "BACK" button on the AV switch repeatedly until the screen displays the HVAC status.

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Operational Check

The purpose of the operational check is to confirm that the system operates properly.

Conditions : Engine running and at normal operating temperature

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1. Set the temperature to 32°C (90°F).
2. Rotate the blower control dial counterclockwise (hold blower control dial until system shuts OFF).
3. Turn ignition switch OFF.
4. Turn ignition switch ON.
5. Press the AUTO switch.
6. Confirm that the set temperature remains at previous temperature.
7. Rotate the blower control dial counterclockwise (hold blower control dial until system shuts OFF).

If NG, go to trouble diagnosis procedure for " MEMORY FUNCTION ".

If OK, continue with next check.

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System Operation

The mode door position (vent, B/L, foot, and defrost) is set by the front air control by means of the mode door motor. When a mode door position is selected on the front air control, voltage is applied to one circuit of the mode door motor while ground is applied to the other circuit, causing the mode door motor to rotate. The direction of rotation is determined by which circuit has voltage applied to it, and which one has ground applied to it. The front air control monitors the mode door position by measuring the voltage signal on the PBR circuit. In AUTO mode the mode door position is set by the front air control which determines the proper position based on inputs from the in-vehicle sensor, ambient sensor, optical sensor, intake sensor, and the temperature selected by the driver or passenger.

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The front air control receives data from the temperature selected by the driver and front and rear passengers. The front air control then applies a voltage to one circuit of the appropriate air mix door motor, while ground is applied to the other circuit, causing the appropriate air mix door motor to rotate. The direction of rotation is determined by which circuit has voltage applied to it, and which one has ground applied to it. The front air control monitors the air mix door positions by measuring the voltage signal on the PBR circuits of each door. In AUTO mode the air mix, intake, mode door, and defrost door positions are set by the front air control which determines the proper position based on inputs from the in-vehicle sensor, ambient sensor, optical sensor, intake sensor, and the temperature selected by the driver and front and rear passengers.

Subsequently, HOT/COLD or DEFROST/VENT or FRESH/RECIRCULATION operation is selected. The new door position data is returned to the front air control.

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The intake door control determines the intake door (driver and passenger) positions based on the position of the recirculation switch. When the recirculation switch is depressed the intake door motors rotate closing off the fresh air inlet and recirculating the cabin air. If the recirculation switch is depressed again, the intake door motors rotate in the opposite direction, again allowing fresh air into the cabin.

In the AUTO mode, the front air control determines the intake doors positions based on the ambient temperature, the intake air temperature and the in-vehicle temperature. When the DEFROST, or OFF switches are pushed or A/C switch is OFF, the front air control sets the intake doors at the fresh position. Recirculation is not allowed in DEFROST, D/F, or Floor modes.

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The front air control determines defroster door position based on the position of the defroster switch. When the defroster switch is depressed, the defroster door motor rotates directing air to the defroster ducts. When any mode other than defroster is selected, the defroster motor rotates in the opposite direction closing off air flow to the defroster ducts.

In the AUTO mode, the front air control determines defroster door position based on the ambient temperature, the intake air temperature and the in-vehicle temperature. Auto mode may be floor/defrost mode, but full defrost mode is only a manually selected mode.

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SYSTEM DESCRIPTION

The front air control controls compressor operation based on ambient and intake temperature and a signal from ECM.

The heater pump improves heater performance specifically at idle conditions. It is designed to operate in either of the following 2 situations

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1. Front blower motor set to maximum speed and temperature control dial (driver or passenger) set to full hot 32°C (90°F) or
2. Engine coolant temperature (signal via CAN communication) minus heater core outlet temperature (intake sensor input to front air control) is greater than 20°C (68°F). If the difference is less than 16°C (61°F), the heater pump will not operate unless the conditions in item No. 1 above are met.

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1. CHECK POWER SUPPLY TO HEATER PUMP Disconnect heater pump connector. Turn ignition switch ON. Set front blower motor to maximum speed. Turn temperature control dial (passenger or driver) to full hot 32°C (90°F). Check voltage between heater pump harness connector E127 terminal (+) and ground. (+) - Ground : Battery voltage OK or NG OK : GO TO 2. NG : GO TO 3 .
2. CHECK HEATER PUMP GROUND Turn ignition switch OFF. Check continuity between heater pump harness connector E127 terminal (-) and ground. (-) - Ground : Continuity should exist. OK or NG OK : Replace heater pump. Refer to " «HEATER PUMP»(ref-259754-S17030050692007080400000) ". NG : Repair harness or connector.
3. CHECK HEATER PUMP RELAY Turn ignition switch OFF. Check heater pump relay. Refer to " «HEATER PUMP RELAY»(ref-259754-S23011639842007080400000) ". OK or NG OK : GO TO 4. NG : Replace heater pump relay.
4. CHECK RELAY POWER SUPPLY Turn ignition switch ON. Check voltage between heater pump relay harness connector E128 terminals 1, 5 and ground. 1 - Ground : Battery voltage 5 - Ground : Battery voltage OK or NG OK : GO TO 5. NG : Repair harness or connector.
5. CHECK HEATER PUMP MOTOR POWER CIRCUIT Turn ignition switch OFF. Check continuity between heater pump relay harness connector (A) E128 terminal 3 and heater pump harness connector (B) E127 terminal (+). 3 - (+) : Continuity should exist. Check continuity between heater pump relay harness connector (A) E128 terminal 3 and ground. 3 - Ground : Continuity should not exist. OK or NG OK : GO TO 6. NG : Repair harness or connector.
6. CHECK CIRCUIT BETWEEN HEATER PUMP RELAY AND FRONT AIR CONTROL Disconnect front air control connector. Check continuity between front air control harness connector (A) M49 terminal 25 and heater pump relay harness connector (B) E128 terminal 2. 2 - 25 : Continuity should exist. Check continuity between heater pump relay harness connector (B) E128 terminal 2 and ground. 2 - Ground : Continuity should not exist. OK or NG OK : Replace front air control. Refer to " «FRONT AIR CONTROL»(ref-259754-S32069075902007080400000) ". NG : Repair harness or connector.

COMPONENT DESCRIPTION

The optical sensor is located on the passenger side defroster grille. It detects sunload entering through windshield by means of a photo diode. The sensor converts the sunload into a current value which is then input into the front air control

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BREAK-IN OPERATION

When replacing compressor clutch assembly, always conduct the break-in operation. This is done by engaging and disengaging the clutch about 30 times. Break-in operation raises the level of transmitted torque.