Nissan Sentra B18 (2020-2025) Service Manual / Ventilation, Heater & Air Conditioner / Heater & Air Conditioning Control System :: Automatic Air Conditioner / Symptom Diagnosis

Nissan Sentra B18 (2020-2025) Service Manual: Symptom Diagnosis

Heater and Air Conditioning System Control Symptoms

Diagnosis Chart by Symptom

Diagnosis Chart By Symptom

Note:

Perform the self-diagnoses with CONSULT before performing the symptom diagnosis. If DTC is detected, perform the corresponding diagnosis.

Symptom		Corresponding malfunction part	Reference
Air conditioning does not activate. Air conditioning cannot be controlled. Operation status of air conditioning is not indicated on display.		A/C auto amp. ignition power supply circuit A/C switch assembly A/C auto amp.	Refer to Diagnosis Procedure.
Air outlet does not change. Mode door motor does not operate normally.		Circuit between mode door motor and A/C auto amp. Mode door motor control linkage Mode door motor A/C auto amp.	Refer to DTC Diagnosis Procedure.
Discharge air temperature of driver side does not change. Air mix door motor LH does not operate normally.		Circuit between air mix door motor LH and A/C auto amp. Air mix door motor LH installation condition Air mix door motor LH A/C auto amp.	Refer to DTC Diagnosis Procedure.
Discharge air temperature of passenger side does not change. Air mix door motor RH does not operate normally.		Circuit between air mix door motor RH and A/C auto amp. Air mix door motor RH installation condition Air mix door motor RH A/C auto amp.	Refer to DTC Diagnosis Procedure.
Intake door does not change. Intake door motor does not operate normally.		Circuit between intake door motor and A/C auto amp. Intake door motor control linkage Intake door motor A/C auto amp.	Refer to DTC Diagnosis Procedure.
Blower motor operation is malfunctioning.		Power supply system of blower motor Circuit between blower motor and A/C auto amp. Blower motor A/C auto amp.	Refer to Diagnosis Procedure
Compressor does not operate.		Circuit between magnet clutch and IPDM E/R Magnet clutch IPDM E/R Circuit between ECM and refrigerant pressure sensor Refrigerant pressure sensor CAN communication circuit A/C auto amp.	Refer to Diagnosis Procedure.
Insufficient cooling. No cool air comes out. (Air flow volume is normal.)		Magnet clutch control system Drive belt slipping Refrigerant cycle ECV (electrical control valve) Air leakage from each duct A/C auto amp. connection recognition signal circuit Temperature setting trimmer (front)	Refer to Diagnosis Procedure.
Insufficient heating. No warm air comes out. (Air flow volume is normal.)		Engine cooling system Heater hose Heater core Air leakage from each duct Temperature setting trimmer (front)	Refer to Diagnosis Procedure.
Noise is heard when front air conditioning system operates.	During A/C compressor operation	Refrigerant cycle	Refer to Symptom Table.
Noise is heard when front air conditioning system operates.	During blower motor operation	Mixing any foreign object in blower motor Blower motor fan breakage Blower motor rotation inferiority	Refer to Component Inspection (Blower Motor).
Memory function does not operate. Setting temperature is not memorized.		Battery power supply system of A/C auto amp. A/C auto amp.	Refer to Diagnosis Procedure.

Insufficient Cooling

Diagnosis Procedure

Diagnosis Procedure

Symptom

Insufficient cooling
No cool air comes out. (Air flow volume is normal.)

Note:

Perform self-diagnoses with CONSULT before performing symptom diagnosis. If any DTC is detected, perform the corresponding diagnosis.

CHECK MAGNET CLUTCH OPERATION
1. 1. Ignition switch ON.
  2. Operate fan switch.
  3. Press A/C switch.
  4. Check that A/C indicator turns ON. Check visually and by sound that A/C compressor operates.
  5. Press A/C switch again.
  6. Check that A/C indicator turns OFF. Check that A/C compressor stops.
Is the inspection result normal?
YES >>
GO TO 2.
NO >>
Perform diagnosis of “COMPRESSOR DOES NOT OPERATE” in “SYMPTOM DIAGNOSIS”. Refer to Diagnosis Procedure.
CHECK DRIVE BELT
1. Check tension of drive belt. Refer to Inspection.
Is the inspection result normal?
YES >>
GO TO 3.
NO >>
Adjust or replace drive belt depending on the inspection results.
CHECK REFRIGERANT CYCLE
1. Connect recovery/recycling recharging equipment to the Nissan Sentra vehicle and perform pressure inspection with gauge. Refer to Symptom Table.
Is the inspection result normal?
YES >>
GO TO 4.
NO >>
Repair or replace parts depending on the inspection results.
CHECK AIR LEAKAGE FROM EACH DUCT
1. Check duct and nozzle, etc. of the front air conditioning system for leakage.
Is the inspection result normal?
YES>>
GO TO 5.
NO>>
Repair or replace parts depending on the inspection results.
CHECK AMBIENT TEMPERATURE DISPLAY
1. Check that there is not much difference between actual ambient temperature and indicated temperature on information display in combination meter.
Is the inspection result normal?
YES >>
GO TO 6.
NO >>
Perform diagnosis for the ambient temperature sensor. Refer to Diagnosis Procedure.
CHECK SETTING OF TEMPERATURE SETTING TRIMMER (FRONT)
1. 1. Check setting value of temperature setting trimmer (front). Refer to Temperature Setting Trimmer.
  2. Check that temperature setting trimmer (front) is set to “+ direction”.
    Note:
    The control temperature can be set with the setting of the temperature setting trimmer (front).
  3. Set difference between set temperature and control temperature to “0”.
Is inspection result normal?
YES >>
Inspection End.
NO >>
Replace A/C auto amp. Refer to Removal and Installation.

Insufficient Heating

Diagnosis Procedure

Diagnosis Procedure

Symptom

Insufficient heating
No warm air comes out. (Air flow volume is normal.)

Note:

Perform self-diagnosis with CONSULT before performing symptom diagnosis. If DTC is detected, perform the corresponding diagnosis.

CHECK COOLING SYSTEM
1. 1. Check engine coolant level and check leakage. Refer to Inspection.
  2. Check reservoir tank cap. Refer to Inspection.
  3. Check water flow sounds of the engine coolant. Refer to Inspection.
Is the inspection result normal?
YES >>
GO TO 2.
NO >>
Refill engine coolant and repair or replace parts depending on the inspection results.
CHECK HEATER HOSE
1. Check installation of heater hose visually or by touching.
Is the inspection result normal?
YES >>
GO TO 3.
NO >>
Repair or replace parts depending on the inspection results.
CHECK HEATER CORE
1. 1. Check temperature of inlet hose and outlet hose of front heater core.
  2. Check that inlet side of heater core is hot and the outlet side is slightly lower than/almost equal to the inlet side.
    
    CAUTION:
    
    Always perform the temperature inspection in a short period of time because the engine coolant temperature is very hot.
Is the inspection result normal?
YES >>
GO TO 4.
NO >>
Replace heater core. Refer to Removal and Installation.
CHECK AIR LEAKAGE FROM EACH DUCT
1. Check duct and nozzle, etc. of front air conditioning system for air leakage.
Is the inspection result normal?
YES>>
GO TO 5.
NO>>
Repair or replace parts depending on the inspection results.
CHECK SETTING OF TEMPERATURE SETTING TRIMMER (FRONT)
1. 1. Check setting value of temperature setting trimmer (front). Refer to Temperature Setting Trimmer.
  2. Check that temperature setting trimmer (front) is set to “− direction”.
    Note:
    The control temperature can be set by the temperature setting trimmer (front).
  3. Set difference between the set temperature and control temperature to “0”.
Are the symptoms solved?
YES >>
Inspection End.
NO >>
Replace A/C auto amp. Refer to Removal and Installation.

Compressor Does Not Operate

Diagnosis Procedure

Diagnosis Procedure

Symptom: A/C compressor does not operate.

Note:

Perform self-diagnoses with CONSULT before performing symptom diagnosis. If DTC is detected, perform the corresponding diagnosis.
Check that refrigerant system is properly charged. If refrigerant amount is below the proper amount, perform inspection of refrigerant leakage.

CHECK MAGNET CLUTCH OPERATION
1. Check magnet clutch. Refer to Component Function Check.
Does it operate normally?
YES >>
GO TO 2.
NO >>
Repair or replace malfunctioning parts.
CHECK REFRIGERANT PRESSURE SENSOR
1. Check refrigerant pressure sensor.
Is the inspection result normal?
YES >>
GO TO 3.
NO >>
Repair or replace malfunctioning parts.

CHECK A/C AUTO AMP. OUTPUT SIGNAL

CONSULT

Select “COMP REQ SIG” and “FAN REQ SIG” in “Data Monitor” mode of “HVAC”.

Monitor item	Condition		Status
COMP REQ SIG	A/C switch	ON	On
COMP REQ SIG	A/C switch	OFF	Off
FAN REQ SIG	Blower motor	ON	On
FAN REQ SIG	Blower motor	OFF	Off

Is the inspection result normal?

YES >>

GO TO 4.

NO >>

Replace A/C auto amp. Refer to Removal and Installation.

CHECK ECM INPUT SIGNAL

CONSULT

Select “AIR COND SIG” and “HEATER FAN SW” in “Data Monitor” mode of “ENGINE”.

Monitor item	Condition		Status
AIR COND SIG	A/C switch	ON	On
AIR COND SIG	A/C switch	OFF	Off
HEATER FAN SW	Blower motor	ON	On
HEATER FAN SW	Blower motor	OFF	Off

Is the inspection result normal?

YES>>

GO TO 5.

NO>>

Check CAN communication system. Refer to Trouble Diagnosis Flow Chart.

CHECK IPDM E/R INPUT SIGNAL

CONSULT

Start engine.

Select “Compressor request 1” in “Data Monitor” mode of “IPDM E/R”.

Monitor item	Condition		Status
Compressor request 1	A/C switch	ON	On
Compressor request 1	A/C switch	OFF	Off

Is the inspection result normal?

YES >>

Inspection End.

NO >>

Check CAN communication system. Refer to Trouble Diagnosis Flow Chart.

 Intake Sensor

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