Automatic Air Conditioner: Overview Nissan Altima L31

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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Overview Air Conditioner LAN Control System

The LAN system consists of auto amp., air mix door motor and mode door motor.

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

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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, DEFROST/VENT or FRESH/RECIRCULATION operation is selected. The new selection data is returned to the auto amplifier.

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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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CAN Communication System Description

CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. Many electronic control units are equipped onto a vehicle, and each control unit shares information and links with other control units during operation (not independent). In CAN communication, control units are connected with 2 communication lines (CAN H line, CAN L line) allowing a high rate of information transmission with less wiring. Each control unit transmits/receives data but selectively reads required data only.

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1. Measure voltage between each terminal and body ground by following charts under "AUTO AMP. INSPECTION TABLE".

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DESCRIPTION

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 TEMP dial right or left, 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 switch 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 turning the TEMP dial. : GO TO 2.
2. STEP 1 - 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 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 TO 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 TO 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. Discharge air flow OK or NG OK: GO TO 9. NG: Air outlet does not change. Go to «MODE DOOR MOTOR CIRCUIT»(ref-206580-S18651121222005112500000) . Intake door does not change. Go to «INTAKE DOOR MOTOR CIRCUIT»(ref-206580-S38631518982005112500000) . Blower motor operation is malfunctioning. Go to «BLOWER MOTOR CIRCUIT»(ref-206580-S13397563942005112500000) . Magnet clutch does not engage. Go to «MAGNET CLUTCH CIRCUIT»(ref-206580-S27395998002005112500000) . Discharge air temperature does not change. Go to «AIR MIX DOOR MOTOR CIRCUIT»(ref-206580-S17906784782005112500000) .
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-206580-S30740258932005112500000) .
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-206580-S25785020992005112500000) .
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)]" (AUTO) switch ON. END NG: Go to «INTAKE SENSOR CIRCUIT»(ref-206580-S27446366942005112500000) .
13. CHECK MALFUNCTIONING SENSOR NOTE: A blinking mark (-) preceding the Code No. indicates a short circuit. No blinking mark (-) preceding the Code No. indicates an open 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. When conducting indoors, direct light (more 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

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 DEFROST/VENT or FRESH/RECIRCULATION operation is selected. The new selection data is returned to the auto amplifier.

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The mode door motor is attached to the heater and cooling 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 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 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 or FRESH/RECIRCULATION operation is selected. The new selection data is returned to the auto amplifier.

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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.

SYSTEM DESCRIPTION

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

COMPONENT DESCRIPTION

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 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.