Automatic Air Conditioner: Overview Nissan Maxima A34

A/C Identification Label

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

Note. Vehicles with factory installed fluorescent dye have a green label.

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Description of Air Conditioner LAN Control System

The LAN (Local Area Network) system consists of unified meter and A/C amp., mode door motor, air mix door motor and intake door motor.

A configuration of these components is shown in the figure below.

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OPERATION

The unified meter and A/C amp. sends mode door, air mix door and intake door opening angle data to the mode door motor LCU, air mix door motor LCU and intake door motor LCU.

The mode door motor, air mix door motor and intake door motor read their respective signals according to the address signal. Opening angle indication signals are sent from the unified meter and A/C amp. to each of the motors and are compared by the LCUs in each motor with the existing position and opening angles. Subsequently, HOT/COLD, DEFROST/VENT or FRESH/RECIRCULATION operation is selected. When the selected angle position is reached a reply is sent form the motors back to the unified meter and A/C amp.

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Description of Control System

The control system consists of input sensors, switches, the unified meter and A/C amp. (microcomputer) and outputs.

The relationship of these components is shown in the figure below

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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 "BCM" on "SELECT SYSTEM" screen. If "BCM" is not indicated, go to «CONSULT-II DATA LINK CONNECTOR (DLC) CIRCUIT»(ref-233642-S33893762202006052600000).

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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 REFERENCE CHART 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 item will be monitored.
6. Touch "RECORD" while monitoring, then the status of the monitored item can be recorded. To stop recording, touch "STOP".

DESCRIPTION

The self-diagnostic system diagnoses sensors, door motors, blower motor, etc. by system line. Refer to applicable sections (items) for details. Shifting from usual control to the self-diagnostic system is accomplished by starting the engine (turning the ignition switch ON) and pressing OFF switch for at least 5 seconds. The "OFF" switch must be pressed within 10 seconds after starting the engine (ignition switch is turned ON). This system will be canceled by either pressing AUTO switch or turning the ignition switch OFF. Shifting from one step to another is accomplished by means of pressing the temperature switch (driver side), as required. Additionally shifting from STEP 5 to AUXILIARY MECHANISM is accomplished by means of pressing the top of the fan) switch.

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1. ENTER SELF-DIAGNOSTIC MODE Turn ignition switch ON. Enter self-diagnostic mode as follows. Within 10 seconds after starting engine (ignition switch is turned ON), press OFF switch for at least 5 seconds. CAUTION: If battery voltage drops below 12 V during diagnosis STEP 3, actuator speed becomes slower and as a result, the system may generate an error even when operation is usual. To avoid this, start engine before performing this diagnosis. Former STEP 1 (LEDs and display screen are checked) no longer exist in this self-diagnosis function. : GO TO 2 .
2. SELF-DIAGNOSIS STEP 2: SENSOR CIRCUITS ARE CHECKED FOR OPEN OR SHORT CIRCUIT Does code No. 20 appear on the display 25 seconds after "2" is illuminated? YES or NO YES: GO TO 3 . NO: GO TO 3 .
3. CHECK OPERATION OF TEMPERATURE SWITCH Press top of temperature switch (driver side). Does the temperature switch advance to self-diagnosis STEP 3? YES or NO YES: GO TO 4. NO: Malfunctioning temperature switch.: Replace A/C switch. Refer to «REMOVAL AND INSTALLATION»(ref-233653-S40720475752006052600000)
4. CHECK TO RETURN SELF-DIAGNOSIS STEP 2 Press bottom of temperature switch (driver side). Does the temperature switch return to self-diagnosis STEP 2? YES or NO YES: GO TO 5. NO: Malfunctioning temperature switch.: Replace A/C switch. Refer to «REMOVAL AND INSTALLATION»(ref-233653-S40720475752006052600000)
5. SELF-DIAGNOSIS STEP 3: MODE DOOR AND INTAKE DOOR POSITIONS ARE CHECKED Press top of temperature switch (driver side). Does code No. 30 appear on the display 50 seconds after "3" is illuminated? YES or NO YES: GO TO 6 . NO: GO TO 4 .
6. STEP 4: CHECK OPERATION OF EACH ACTUATOR Press top of temperature switch (driver side). Press DEF switch. Code No. (a "4" followed by a 1, 2, 3, etc., through 6) of each actuator test is indicated on the display. : GO TO 7 .
7. CHECK ACTUATORS Refer to the following chart and confirm discharge air flow, air temperature, blower motor voltage and compressor operation. ACTUATOR TEST CODES Actuator test code no. 41 42 43 44 45 46 Mode door position VENT B/L 1 B/L 2 FOOT (1) D/F DEF Intake door position REC REC 20% FRE FRE FRE FRE Air mix door position FULL COLD FULL COLD FULL HOT FULL HOT FULL HOT FULL HOT Blower motor voltage (approx.) 5.25V 12.70V 8.75V 8.75V 8.75V 12.70V Compressor ON ON OFF OFF ON ON (1) *1: FOOT position during automatic control. Refer to " «AUXILIARY MECHANISM: FOOT POSITION SETTING TRIMMER»(ref-233653-S08989646472006052600000) ". Checks must be made visually, by listening to any noise, or by touching air outlets with your hand, etc. for improper operation. OK or NG OK: GO TO 8. NG: Air outlet does not change. Go to «MODE DOOR MOTOR CIRCUIT»(ref-233653-S37461661582006052600000). Intake door does not change. Go to «INTAKE DOOR MOTOR CIRCUIT»(ref-233653-S04359640312006052600000). Blower motor operation is malfunctioning. Go to «BLOWER MOTOR CIRCUIT»(ref-233653-S05563777972006052600000). Magnet clutch does not engage. Go to «MAGNET CLUTCH CIRCUIT»(ref-233653-S19758029252006052600000). Discharge air temperature does not change. Go to «AIR MIX DOOR MOTOR CIRCUIT»(ref-233653-S24079222972006052600000).
8. SELF-DIAGNOSIS STEP 5: TEMPERATURE OF EACH SENSOR IS CHECKED Press top of the temperature switch (driver side). Code No. 51 appears on the display. : GO TO 9 .
9. CHECK AMBIENT SENSOR Press (DEF) switch one time. Temperature detected by ambient sensor is indicated on the display (°F for U.S.A. model, °C for Canada model). NOTE: If temperature shown on display greatly differs from actual temperature, check sensor circuit first, then inspect sensor. OK or NG OK: GO TO 10. NG: Go to «AMBIENT SENSOR CIRCUIT»(ref-233653-S00383610032006052600000).
10. CHECK IN-VEHICLE SENSOR Press (DEF) switch a second time. Temperature detected by in-vehicle sensor is indicated on the display (°F for U.S.A. model, °C for Canada model). NOTE: If temperature shown on display greatly differs from actual temperature, check sensor circuit first, then inspect sensor. OK or NG OK: GO TO 11. NG: Go to «IN-VEHICLE SENSOR CIRCUIT»(ref-233653-S05864166492006052600000).
11. CHECK INTAKE SENSOR Press (DEF) switch a third time. Temperature detected by intake sensor is indicated on the display (°F for U.S.A. model, °C for Canada model). NOTE: If temperature shown on display greatly differs from actual temperature, check sensor circuit first, then inspect sensor. OK or NG OK: GO TO 12. NG: Go to «INTAKE SENSOR CIRCUIT»(ref-233653-S41784476492006052600000).
12. CHECK CAN COMMUNICATION ERROR Press (REC) switch. CAN communication error between unified meter and A/C amp. and DISPLAY UNIT or DISPLAY CONTROL UNIT is detected. OK or NG OK: Turn ignition switch OFF or AUTO switch ON. END NG: Go to CAN communication. Refer to «CAN COMMUNICATION SYSTEM DESCRIPTION»(ref-233665-S00174890062006052600000). Unified meter and A/C amp. - DISPLAY UNIT Unified meter and A/C amp. - DISPLAY CONTROL UNIT CHECK MALFUNCTIONING SENSOR Refer to the following chart for malfunctioning code No. (If two or more sensors malfunction, corresponding code Nos. blink respectively twice.) When conducting indoors, aim a light (more than 60W) at sunload sensor, otherwise Code No. 25 will indicate despite that sunload sensor is functioning properly.: Inspection End. CHECK MALFUNCTIONING DOOR MOTOR POSITION SWITCH Mode and/or intake door motor PBR(s) malfunctioning.

Operational Check

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

Conditions: Engine running and at usual operating temperature

System Operation

The unified meter and A/C amp. receives data from each of the sensors. The unified meter and A/C amp. sends air mix door, mode door and intake door opening angle data to the air mix door motor LCU, mode door motor LCU and intake door motor LCU.

The air mix door motor, mode door motor and intake door motor read their respective signals according to the address signal. Opening angle indication signals received from the unified meter and A/C amp. and each of the motor position sensors are compared by the LCUs in each motor with the existing decision and opening angles. Subsequently, HOT/COLD or DEFROST/VENT or FRESH/RECIRCULATION operation is selected. The new selection data is returned to the unified meter and A/C amp.

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The unified meter and A/C amp. receives data from each of the sensors. The unified meter and A/C amp. sends air mix door, mode door and intake door motor opening angle data to the air mix door motor LCU, mode door motor LCU and intake door motor LCU.

The air mix door motor, mode door motor and intake door motor read their respective signals according to the address signal. Opening angle indication signals received from the unified meter and A/C amp. and each of the motor position sensors are compared by the LCUs in each motor with the existing decision and opening angles. Subsequently, HOT/COLD or DEFROST/VENT or FRESH/RECIRCULATION operation is selected. The new selection data is returned to the unified meter and A/C amp.

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The intake door control determines intake door position 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 unified meter and A/C amp. sets the intake door at the FRESH position.

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SYSTEM DESCRIPTION

Unified meter and A/C amp. controls compressor operation by ambient temperature and signal from ECM.

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.

See also:
• IDLE SPEED AND IGNITION TIMING CHECK