Subaru Outback (BR): Basic Diagnostic Procedure of HVAC System

A: PROCEDURE

NOTE: When the sunload sensor check is performed indoors or in the shade, it could be diagnosed as sensor having an open circuit. Always perform the inspection in direct sunlight.

General Description

A: CAUTION

1) Never connect the battery in reverse polarity.

• Doing so may immediately damage the A/C CM.

2) Do not disconnect the battery terminals while the engine is running.

• A large counter electromotive force will be generated in the generator, and this voltage may damage electronic parts such as A/C CM etc.

3) Before disconnecting the connectors of sensors and the A/C CM, be sure to turn off the ignition switch.

• A/C CM may be damaged.

4) Every A/C-related part is a precision part. Do not drop them.

5) Airbag system wiring harness is routed near the A/C control panel and junction box.

CAUTION:

• Do not use electrical test equipment on the airbag system wiring harness and connector.
• Be careful not to damage the airbag system wiring harness when servicing the A/C control panel and junction box.

B: INSPECTION

Before performing the diagnosis, check the following items which may cause problems in the A/C system.

1. BATTERY

Check the battery. <Ref. to SC(H4SO)-28, INSPECTION, Battery.>

NOTE: If the battery voltage does not reach the specified value, recharge or replace the battery.

C: PREPARATION TOOL

1. SPECIAL TOOL

2. GENERAL TOOL

Electrical Component Location

A: LOCATION

1. ENGINE COMPARTMENT

1. A/C compressor
2. A/C relay
3. Pressure sensor
4. Ambient sensor

2. COMPARTMENT

1. Evaporator sensor
2. Air mix door actuator*1 or air mix door actuator (driver's seat)*2
3. A/C CM
4. Blower motor
5. Sunload sensor
6. Intake door actuator
7. Mode door actuator
8. In-vehicle sensor
9. A/C control panel
10. Air mix door actuator (passenger's seat)*2

*1: Manual A/C
*2: Auto A/C

Control Module I/O Signal

A: ELECTRICAL SPECIFICATION

*1: Battery voltage cannot be measured because of digital signal.
*2: Manual A/C
*3: Auto A/C

B: WIRING DIAGRAM

<Ref. to WI-53, WIRING DIAGRAM, Air Conditioning System.>

Diagnostic Chart for Self-Diagnosis

A: OPERATION

1. Defroster switch
2. Rear window defogger switch
3. Mode change switch
4. A/C switch
5. FAN switch
6. OFF switch
7. FRESH/RECIRC switch
8. Temperature control switch (for driver's seat)
9. Temperature control switch (for passenger's seat)
10. AUTO switch
11. DUAL switch

1. A/C CONTROL SYSTEM SELF-DIAGNOSIS

2. SENSOR CHECK TABLE

NOTE:

• When the sunload sensor check is performed indoors or in the shade, it could be diagnosed as having an open circuit. Always check the sunload sensor with the sun shining on it.
• When currently malfunctioning, AUTO flashes on display.
• Past malfunction can be cleared by disconnecting the battery ground cable.

*1: Displays current malfunction only.

3. OPERATING MODE TABLE

4. DIAGNOSTIC PROCEDURE WHEN SELF DIAGNOSIS USING A/C CONTROL PANEL DOES NOT OPERATE

NOTE: For diagnostic procedure, refer to "Nothing is displayed on the screen or indicators do not illuminate." in Diagnostics with Phenomenon. <Ref. to AC(diag)-14, NOTHING IS DISPLAYED ON THE SCREEN OR INDICATORS DO NOT ILLUMINATE., DIAGNOSTIC PROCEDURE WITH PHENOMENON, Diagnostics with Phenomenon.>

Diagnostics with Phenomenon

A: INSPECTION

1. Perform diagnosis according to the diagnosis procedure for the corresponding symptom listed in the symptom table.

2. If there are multiple symptoms, perform the diagnosis in the order of symptom number (1 → 2 →... → 13).

1. SYMPTOM TABLE

B: DIAGNOSTIC PROCEDURE WITH PHENOMENON

1. NOTHING IS DISPLAYED ON THE SCREEN OR INDICATORS DO NOT ILLUMINATE.

TROUBLE SYMPTOM:

• When the AUTO button is pressed with IGN ON, nothing is displayed on the screen or indicators do not illuminate.
• Self diagnosis using A/C control panel does not operate.

Trouble causes:

• Control module power supply circuit failure
• A/C control panel power supply failure
• UART communication failure

WIRING DIAGRAM:

• Auto A/C

• Manual A/C

2. AIR CONDITIONER DOES NOT STOP EVEN WHEN THE OFF SWITCH IS PRESSED. (VEHICLES WITH FULLY AUTOMATIC AIR CONDITIONER)

TROUBLE SYMPTOM:

Even when the OFF switch is pressed, the blower fan does not turn off, the inlet opening remains in FRESH mode, and the compressor does not turn off.

Trouble causes:

• UART communication failure
• A/C control panel failure
• Blower motor failure
• Intake door actuator failure
• Compressor failure

3. THE WINDSHIELD GLASS IS NOT CLEARED EVEN WHEN THE DEF SWITCH IS PRESSED. (VEHICLES WITH FULLY AUTOMATIC AIR CONDITIONER)

TROUBLE SYMPTOM:

Even when the DEF switch is pressed, the defroster indicator does not illuminate, the outlet opening is not set to DEF, the compressor does not turn on and the outlet opening is not set to FRESH.

Trouble causes:

• UART communication failure
• A/C control panel failure
• Mode door actuator failure
• Compressor failure
• Intake door actuator failure

4. COLD AIR NOT EMITTED

TROUBLE SYMPTOM:

Cold air not emitted.

Trouble causes:

• Airflow capacity failure
• Refrigerant pressure failure
• Air mix actuator (driver's) failure
• Air mix actuator (passenger's) failure (with left/right independent air conditioner only)
• Intake door actuator failure
• Evaporator sensor failure (vehicles with automatic air conditioner only)
• In-vehicle sensor failure (vehicles with automatic air conditioner only)
• Ambient sensor failure (vehicles with automatic air conditioner only)
• Sunload sensor failure (vehicles with automatic air conditioner only)

5. WARM AIR NOT EMITTED

TROUBLE SYMPTOM:

Warm air not emitted.

Trouble causes:

• Airflow capacity failure
• Coolant failure
• UART communication failure
• A/C control panel failure
• Air mix actuator (driver's) failure
• Air mix actuator (passenger's) failure (with left/right independent air conditioner only)
• Intake door actuator failure
• Evaporator sensor failure (vehicles with automatic air conditioner only)
• In-vehicle sensor failure (vehicles with automatic air conditioner only)
• Ambient sensor failure (vehicles with automatic air conditioner only)
• Sunload sensor failure (vehicles with automatic air conditioner only)

6. COMPARTMENT TEMPERATURE IS EXCESSIVELY LOWER THAN SETTING TEMPERATURE

TROUBLE SYMPTOM:

Compartment temperature is excessively lower than setting temperature.

Trouble causes:

• Large airflow capacity
• Refrigerant pressure failure
• UART communication failure
• A/C control panel failure
• Air mix actuator (driver's) failure
• Air mix actuator (passenger's) failure (with left/right independent air conditioner only)
• Evaporator sensor failure (vehicles with automatic air conditioner only)
• In-vehicle sensor failure (vehicles with automatic air conditioner only)
• Ambient sensor failure (vehicles with automatic air conditioner only)
• Sunload sensor failure (vehicles with automatic air conditioner only)

7. COMPARTMENT TEMPERATURE IS EXCESSIVELY HIGHER THAN SETTING TEMPERATURE

TROUBLE SYMPTOM:

Compartment temperature is excessively higher than setting temperature.

Trouble causes:

• Large airflow capacity
• UART communication failure
• A/C control panel failure
• Air mix actuator (driver's) failure
• Air mix actuator (passenger's) failure (with left/right independent air conditioner only)
• Intake door actuator failure
• Evaporator sensor failure (vehicles with automatic air conditioner only)
• In-vehicle sensor failure (vehicles with automatic air conditioner only)
• Ambient sensor failure (vehicles with automatic air conditioner only)
• Sunload sensor failure (vehicles with automatic air conditioner only)

8. AIR DOES NOT COME OUT, OR AIRFLOW CAPACITY IS INSUFFICIENT

TROUBLE SYMPTOM:

• Airflow capacity is insufficient.
• No air comes out even when the fan switch or fan dial is operated.
• There is a fan speed at which no air comes out.

Trouble causes:

• Airflow capacity failure
• UART communication failure
• A/C control panel failure
• Blower motor failure

Auto A/C

WIRING DIAGRAM:

Manual A/C

WIRING DIAGRAM:

9. AIR GOES OUT OF CONTROL

TROUBLE SYMPTOM:

• The blower rotates even though the blower switch is not turned on.
• The blower motor continues to rotate at high speed. (Not adjustable.)

Trouble causes:

• Airflow capacity failure
• UART communication failure
• A/C control panel failure
• Blower motor failure

Auto A/C

WIRING DIAGRAM:

Manual A/C

WIRING DIAGRAM:

10.COLD AIR DOES NOT COME OUT EVEN WHEN THE A/C SWITCH IS PRESSED. THE GLASS CANNOT BE DEFOGGED. (COMPRESSOR DOES NOT OPERATE. (VARIABLE) )

TROUBLE SYMPTOM:

Compressor does not operate even when the A/C switch is turned on and the fan switch is set to LO - HI.

Trouble causes:

Compressor failure

WIRING DIAGRAM:

11.UNABLE TO SWITCH SUCTION VENTS

TROUBLE SYMPTOM:

Even when the FRESH/RECIRC switch is pressed, the inlet opening does not switch to RECIRC → FRESH or FRESH → RECIRC.

Trouble causes:

Intake door actuator failure

WIRING DIAGRAM:

12.UNABLE TO SWITCH VENTS

TROUBLE SYMPTOM:

Unable to switch blow vents.

• Auto dual
  Even when the mode switch is operated, outlet opening does not switch to FACE → B/L → FOOT → F/D.
• Manual A/C
  Selected mode does not work even when each mode switch is operated.

Trouble causes:

Mode door actuator failure

13.ILLUMINATION DOES NOT COME ON OR CANNOT DIM

TROUBLE SYMPTOM:

Even when the lighting switch is operated, the illumination does not come on. Even when the illumination control is operated, the illumination does not dim.

TROUBLE SYMPTOM:

Open circuit in illumination circuit

WIRING DIAGRAM:

Diagnostic Procedure for Sensors

A: AMBIENT SENSOR

TROUBLE SYMPTOM:

• Ambient temperature is falsely recognized as 15.2ºC, and the compartment temperature is adjusted.
• DTC"22" Faulty ambient sensor, or communication failure is detected.

Trouble causes:

• Ambient sensor failure
• Ambient sensor circuit failure
• CAN communication circuit failure

WIRING DIAGRAM:

Subaru Select Monitor

A: OPERATION

For details of basic operations, refer to "PC application help for Subaru Select Monitor".

NOTE: When initialization communication using Select Monitor is impossible, perform diagnosis according to "Diagnostic Procedure Used When Abnormal Communication with Subaru Select Monitor Occurs".

Read Diagnostic Trouble Code (DTC)

A: OPERATION

For details concerning the operation procedure, refer to "PC application help for Subaru Select Monitor".

Clear Memory Mode

A: OPERATION

For details concerning the operation procedure, refer to "PC application help for Subaru Select Monitor".

Read Current Data

A: OPERATION

For details concerning the operation procedure, refer to "PC application help for Subaru Select Monitor".

B: LIST

NOTE: For detailed operation procedures, refer to "PC application help for Subaru Select Monitor".

Diagnostic Procedure for Subaru Select Monitor Communication

A: COMMUNICATION FOR INITIALIZING IMPOSSIBLE

DIAGNOSIS:

Defective CAN communication circuit

TROUBLE SYMPTOM:

• LAN system is abnormal.
• Communication failure between Subaru Select Monitor and A/C CM

WIRING DIAGRAM:

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