Automatic A/c Heater System: Overview Nissan Maxima A33

GENERAL INFORMATION

1. The V-6 variable compressor differs from previous units. The vent temperatures of the V-6 variable compress do not drop too far below 5°C (41°F) when: Evaporator intake air temperature is less than 20°C (68°F) Engine is running at speeds less than 1,500 RPM. This is because the V-6 compressor provides a means of "capacity" control.
2. The V-6 variable compressor provides refrigerant control under varying conditions. During cold winters, it may not produce high refrigerant pressure discharge (compared to previous units) when used with air conditioning systems.
3. A "clanking" sound may occasionally be heard during refrigerant charge. The sound indicates that the tilt angle of the swash plate has changed and is not a problem.
4. For air conditioning systems with the V-6 compressor, the clutch remains engaged unless: the system main switch, fan switch or ignition switch is turned OFF. When ambient (outside) temperatures are low or when the amount of refrigerant is insufficient, the clutch is disengaged to protect the compressor.
5. A constant range of suction pressure is maintained when engine speed is greater than a certain value. It normally ranges from 147 to 177 kPa (1.5 to 1.8 kg/cm 2 , 21 to 26 psi) under varying conditions. In previous compressors, however, suction pressure was reduced with increases in engine speed.

AIR CONDITIONER LAN SYSTEM OVERVIEW CONTROL SYSTEM

The LAN system consists of auto amp., air mix door motor, intake door motor and mode door motor. A configuration of these components is shown in the diagram below.

Scheme 1

Operation

The auto amplifier receives data from each of the sensors. The amplifier sends air mix door, intake door and mode door opening angle data to the air mix door motor LCU, mode door LCU and intake door motor LCU. The air mix door motor, intake door motor and mode door motor read their respective signals according to the address signal. Opening angle indication signals received from the auto amplifier 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, FRESH/RECIRCULATION or DEFROST/VENT operation is selected. The new selection data is returned to the auto amplifier.

Scheme 2

OVERVIEW OF CONTROL SYSTEM

The control system consists of input sensors, switches, the automatic amplifier (microcomputer) and outputs. The relationship of these components is shown in the diagram below

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INTRODUCTION AND GENERAL DESCRIPTION (WITHOUT NAVIGATION SYSTEM)

The self-diagnostic system diagnoses sensors, door motors, blower motor, etc. by system line. Refer to applicable sections (items) for details. Shifting from normal control to the self-diagnostic system is accomplished by starting the engine (turning the ignition switch from "OFF" to "ON") and pressing "[OFF]" switch for at least 5 seconds. The "[OFF]" switch must be pressed within 5 seconds after starting the engine (ignition switch is turned "ON"). This system will be canceled by either pressing [(AUTO)] (AUTO) switch or turning the ignition switch "OFF". Shifting from one step to another is accomplished by means of pushing TEMP dial right turn or TEMP dial left turn switch, as required.

Additionally shifting from STEP 5 to AUXILIARY MECHANISM is accomplished by means of pushing (fan) UP switch.

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Perform all of the following tests to narrow the problem to a specific assembly, actuator, or function. Link to the Diagnostic Procedure which corresponds to malfunctions noted in these tests. If the A/C display screen has no display, check all power supply circuits to the A/C Auto Amp.

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1. ENTER SELF-DIAGNOSTIC MODE Perform steps 1 - 3 Turn the ignition OFF. Start the engine. Immediately after starting the engine press and hold the OFF switch (for the auto A/C system) for at least 5 seconds. The A/C Auto Amp. should now be in Self Diagnosis mode. Self Diagnosis steps 1 - 5 can now be performed. Self Diagnosis step 1 will be displayed first. Shifting from one step to another is accomplished by pressing the temperature increase or decrease switch. : GO TO 2.
2. STEP 1 LED/DISPLAY CHECK Verify all segments illuminate. If all segments do not illuminate the fluorescent display tube is malfunctioning or the system has not entered self diagnosis which would indicate a malfunctioning OFF switch. Do all LEDs and segments illuminate? Yes or No Yes: GO TO 3. No: Malfunctioning [OFF] switch, LED or fluorescent display tube. Replace A/C auto amp.
3. CHECK TO ADVANCE SELF-DIAGNOSIS STEP 2 Turn the TEMP dial clockwise. Advance to self-diagnosis STEP 2. If the system does not shift between step 1 and 2, a malfunctioning TEMP dial is indicated. Yes or No Yes: GO TO 4. No: Malfunctioning TEMP dial. Replace A/C auto amp.
4. CHECK TO RETURN SELF-DIAGNOSIS STEP 1 Turn the TEMP dial counterclockwise. Return to self-diagnosis STEP 1. If the system does not shift between step 1 and 2, a malfunctioning TEMP dial is indicated. Yes or No Yes: GO TO 5. No: Malfunctioning TEMP dial. Replace A/C auto amp.
5. STEP 2 - SENSOR CIRCUITS ARE CHECKED FOR OPEN OR SHORT CIRCUIT Turn the TEMP dial clockwise, advance to STEP 2: Wait (about 25 seconds) for two digit Code to appear. This is the Electronic Sensor Input Check which includes circuits. Does code No. 20 appear on the display? Yes or No Yes: GO TO 6. No: GO TO 13 .
6. STEP 3 - MODE DOOR AND INTAKE DOOR POSITIONS ARE CHECKED Turn the TEMP dial clockwise, advance to STEP 3. Wait (about 50 seconds) for two digit Code to appear. This is the Mode Door and Intake Door Position Switch input checks including circuits. Does code No. 30 appear on the display? Yes or No Yes: GO TO 7. No: GO TO 14 .
7. STEP 4 - OPERATION OF EACH ACTUATOR IS CHECKED Turn the TEMP dial clockwise, advance to STEP 4. Engine running. This is Heater and A/C system check. Code 41 will be displayed. Use the DEF switch to advance the code number from 41 to 46. After 46, the display will return to code 41 and can be advanced to 46 again. : GO TO 8.
8. CHECK ACTUATORS Confirm operation of system components according to the following charts. Checks must be made visually, by listening to any noise, or by touching air outlets with your hand, etc. for improper operation. Operating condition of each actuator cannot be checked by indicators. OK or NG OK: GO TO 9. NG Air outlet does not change. Go to " «MODE DOOR MOTOR»(ref-231076-S24852095122006050300000) . Intake door does not change. Go to " «INTAKE DOOR MOTOR»(ref-231076-S30427342222006050300000) 7 Blower motor operation is malfunctioning. Go to " «BLOWER MOTOR»(ref-231076-S06575626952006050300000) Magnet clutch does not engage. Go to " «MAGNET CLUTCH»(ref-231076-S01148830932006050300000) Discharge air temperature does not change. Go to " «AIR MIX DOOR MOTOR»(ref-231076-S09161336042006050300000)
9. STEP 5 - TEMPERATURE OF EACH SENSOR IS CHECKED Turn the TEMP dial clockwise, advance to STEP 5. This is Intake sensor, In Vehicle sensor and Ambient Sensor function check. Code 51 will be displayed. NOTE: Each sensor reading should be approximately the actual temperature. : GO TO 10.
10. CHECK AMBIENT SENSOR Press DEF once, temperature detected by the Ambient Sensor is displayed. OK or NG OK: GO TO 11. NG: Go to «AMBIENT SENSOR CIRCUIT»(ref-231076-S08443754362006050300000)
11. CHECK IN-VEHICLE SENSOR Press DEF second time, temperature detected by the In Vehicle Sensor is displayed. OK or NG OK: GO TO 12. NG: Go to «IN-VEHICLE SENSOR CIRCUIT»(ref-231076-S08588112422006050300000)
12. CHECK INTAKE SENSOR Press DEF third time, temperature detected by the Intake Sensor is displayed. OK or NG OK Press (DEF) switch the fourth time. Display returns to original presentation 51. Turn ignition switch OFF or [(AUTO)] switch ON. END NG: Go to «INTAKE SENSOR CIRCUIT»(ref-231076-S03800301812006050300000)
13. CHECK MALFUNCTIONING SENSOR NOTE: A blinking mark (-) preceding the Code No. indicates a short circuit. If 2 or more items are malfunctioning the corresponding codes will alternately blink twice. A circuit will be detected as open or shorted and its code No. will be displayed when input signals correspond with conditions in the following chart. *1: "95%" and "5%" refer to percentage with respect to stroke of air mix door. (Full cold: 0%, Full hot: 100%) *2: Conduct self-diagnosis STEP 2 under sunshine. When conducting indoors, direct light (move than 60W) at sunload sensor. : INSPECTION END
14. CHECK MALFUNCTIONING DOOR MOTOR POSITION SWITCH 30- Mode door and intake door position switches are in working order. Continue to next step. 31- Mode door circuit / switch in vent position switch is malfunctioning. 32- Mode door circuit / switch in B/L position switch is malfunctioning. 34- Mode door circuit / switch in Foot position switch is malfunctioning. 35- Mode door circuit / switch in Foot Def. Position switch is malfunctioning. 36- Mode door circuit / switch in Def. Position switch is malfunctioning. 37- Intake door mode circuit / switch in Fresh Air position is malfunctioning. 38- Intake door mode circuit / switch in 20% Fresh Air position is malfunctioning. 39- Intake door mode circuit / switch in Recirculation Air position is malfunctioning. NOTE: If 2 or more items are malfunctioning the corresponding codes will alternately blink twice. If the Mode Door Motor harness is disconnected repeated display pattern of 31 --> 32 --> 34 --> 35 --> 36 will occur. If Intake Door Motor harness is disconnected repeated display pattern of 37 --> 38 --> 39 will occur. If any Mode Door Motor Position Switch is malfunctioning the Mode Door Motor will also malfunction. : INSPECTION END

INTRODUCTION AND GENERAL DESCRIPTION (WITH NAVIGATION SYSTEM)

The self-diagnostic system diagnoses sensors, door motors, blower motor, etc. by system line. Refer to applicable sections (items) for details. Shifting from normal control to the self-diagnostic system is accomplished by starting the engine (turning the ignition switch from "OFF" to "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)] (AUTO) switch or turning the ignition switch "OFF". Shifting from one step to another is accomplished by means of turning temperature dial, as required. Additionally shifting from STEP 5 to AUXILIARY MECHANISM is accomplished by means of pushing (fan) UP switch.

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1. SET IN SELF-DIAGNOSTIC MODE Turn ignition switch ON. Set in self-diagnostic mode as follows. Within 10 seconds after starting engine (ignition switch is turned "ON".), press [OFF] switch for at least 5 seconds. : GO TO 2.
2. STEP 1 - ALL LEDs AND DISPLAY SCREEN ARE CHECKED When switch's LED and display are functioning properly in STEP-1, LED and display will come on. OK or NG OK: GO TO 3. NG: Malfunctioning [OFF] switch, LED or fluorescent display tube. Go to " «MAIN POWER SUPPLY AND GROUND CIRCUIT CHECK»(ref-231076-S20031831762006050300000) ", .
3. VERIFY ADVANCE TO SELF-DIAGNOSIS STEP 2 Turn temperature dial clockwise. Does advance to self-diagnosis STEP 2? Yes or No Yes: GO TO 4. No: Malfunctioning temperature dial. Check Display & NAVI control unit.
4. VERIFY RETURN TO SELF-DIAGNOSIS STEP 1 Turn temperature dial counterclockwise. Does return to self-diagnosis STEP 1? Yes or No Yes: GO TO 5. No: Malfunctioning temperature dial. Check Display & NAVI control unit.
5. STEP 2 - SENSOR CIRCUITS ARE CHECKED FOR OPEN OR SHORT CIRCUIT Turn temperature dial clockwise. Does code No. 20 appear on the display? Yes or No Yes: GO TO 6. No: GO TO 14 .
6. STEP 3 - MODE DOOR AND INTAKE DOOR POSITIONS ARE CHECKED Turn temperature dial clockwise. Does code No. 30 appear on the display? Yes or No Yes: GO TO 7. No: GO TO 15 .
7. STEP 4 - OPERATION OF EACH ACTUATOR IS CHECKED Turn temperature dial clockwise. Engine running. Press DEF switch, code No. of each actuator test is indicated on the display. : GO TO 8.
8. CHECK ACTUATORS Confirm operation of system components according to the following charts. Checks must be made visually, by listening to any noise, or by touching air outlets with your hand, etc. for improper operation. Operating condition of each actuator cannot be checked by indicators. OK or NG OK: GO TO 9. NG Air outlet does not change. Go to " «MODE DOOR MOTOR»(ref-231076-S24852095122006050300000) Intake door does not change. Go to " «INTAKE DOOR MOTOR»(ref-231076-S30427342222006050300000) Blower motor operation is malfunctioning. Go to " «BLOWER MOTOR»(ref-231076-S06575626952006050300000) Magnet clutch does not engage. Go to " «MAGNET CLUTCH»(ref-231076-S01148830932006050300000) Discharge air temperature does not change. Go to " «AIR MIX DOOR MOTOR»(ref-231076-S09161336042006050300000)
9. STEP 5 - TEMPERATURE OF EACH SENSOR IS CHECKED Turn temperature dial clockwise. Code No. 51 appears on the display. : GO TO 10.
10. CHECK AMBIENT SENSOR Press (DEF) switch one time, temperature detected by ambient sensor is indicated on the display. ECON shown in display indicates negative temperature reading. 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 «AMBIENT SENSOR CIRCUIT»(ref-231076-S08443754362006050300000)
11. CHECK IN-VEHICLE SENSOR Press (DEF) switch the second time, temperature detected by in-vehicle sensor is indicated on the display screen. ECON shown in display indicates negative temperature reading. 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 «IN-VEHICLE SENSOR CIRCUIT»(ref-231076-S08588112422006050300000)
12. CHECK INTAKE SENSOR Press (DEF) switch the third time, temperature detected by intake sensor is indicated on the display. NOTE: If temperature shown on display greatly differs from actual temperature, check sensor circuit first, then inspect sensor. OK or NG OK: GO TO 13. NG: Go to «INTAKE SENSOR CIRCUIT»(ref-231076-S03800301812006050300000)
13. DETECTS MULTIPLEX COMMUNICATION ERROR Press REC switch. Does code No. 52 appears on the display Yes or No Yes: INSPECTION END No Go to " «MULTIPLEX COMMUNICATION CIRCUIT»(ref-231076-S13919590002006050300000) ", . Go to " «OPERATIONAL CHECK»(ref-231076-S26238954402006050300000) ", . Confirm that A/C system is in good order.
14. CHECK MALFUNCTIONING SENSOR NOTE: A blinking mark (-) preceding the Code No. indicates a short circuit. If 2 or more items are malfunctioning the corresponding codes will alternately blink twice. A circuit will be detected as open or shorted and its code No. will be displayed when input signals correspond with conditions in the following chart. *1: "95%" and "5%" refer to percentage with respect to stroke of air mix door. (Full cold: 0%, Full hot: 100%) *2: Conduct self-diagnosis STEP 2 under sunshine. When conducting indoors, direct light (move than 60W) at sunload sensor. : INSPECTION END
15. CHECK MALFUNCTIONING DOOR MOTOR POSITION SWITCH 30- Mode door and intake door position switches are in working order. Continue to next step. 31- Mode door circuit / switch in vent position switch is malfunctioning. 32- Mode door circuit / switch in B/L position switch is malfunctioning. 34- Mode door circuit / switch in Foot position switch is malfunctioning. 35- Mode door circuit / switch in Foot Def. Position switch is malfunctioning. 36- Mode door circuit / switch in Def. Position switch is malfunctioning. 37- Intake door mode circuit / switch in Fresh Air position is malfunctioning. 38- Intake door mode circuit / switch in 20% Fresh Air position is malfunctioning. 39- Intake door mode circuit / switch in Recirculation Air position is malfunctioning. NOTE: If 2 or more items are malfunctioning the corresponding codes will alternately blink twice. If the Mode Door Motor harness is disconnected repeated display pattern of 31 --> 32 --> 34 --> 35 --> 36 will occur. If Intake Door Motor harness is disconnected repeated display pattern of 37 --> 38 --> 39 will occur. If any Mode Door Motor Position Switch is malfunctioning the Mode Door Motor will also malfunction. : INSPECTION END

OPERATIONAL CHECK

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

System Operation

The auto amplifier receives data from each of the sensors. The amplifier 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 auto amplifier 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 OPEN/CLOSE or DEFROST/VENT operation is selected. The new selection data is returned to the auto amplifier.

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COMPONENT DESCRIPTION

The mode door motor is attached to the heater unit. It rotates so that air is discharged from the outlet set by the auto amplifier. Motor rotation is conveyed to a link which activates the mode door.

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The auto amplifier receives data from each of the sensors. The amplifier sends air mix door, mode door, 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 auto amplifier 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 operation is selected. The new selection data is returned to the auto amplifier.

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The air mix door motor is attached to the heater unit. It rotates so that the air mix door is opened or closed to a position set by the auto amplifier. Motor rotation is then conveyed through a shaft and the air mix door position is then fed back to the auto amplifier by PBR built-in air mix door motor.

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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 ECON, DEFROST, or OFF switches are pushed, the auto amplifier sets the intake door at the "Fresh" position.

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The intake door motor is attached to the intake unit. It rotates so that air is drawn from inlets set by the auto amplifier. Motor rotation is conveyed to a lever which activates the intake door.

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SYSTEM DESCRIPTION

Auto amplifier controls compressor operation by ambient temperature and signal from ECM.

The ambient sensor is attached in front of the right side condenser. It detects ambient temperature and converts it into a resistance value which is then input into the auto amplifier.

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The sunload sensor is located on the right 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 auto amplifier.

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Break-in Operation

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

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1. Drain the cooling system. .
2. Disconnect the two heater hoses from inside the engine compartment.
3. Remove the Blower and cooling unit. Refer to «BLOWER AND COOLING UNIT (A/C EVAPORATOR)»(ref-231076-S02641726722006050300000) .
4. Remove the steering member assembly. .
5. Remove the heater unit.
6. Remove the heater core.