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

Heater and Air Conditioning System Control Symptoms

Symptom Table

Symptom Table

SYMPTOM TABLE

Symptom

Reference Page

A/C system does not come on.

Go to Trouble Diagnosis Procedure for A/C System.

Refer to Diagnosis Procedure.

Air outlet does not change.

Go to Trouble Diagnosis Procedure for Mode Door Motor

Refer to Diagnosis Procedure.

Mode door motor does not operate normally.

Discharge air temperature does not change.

Go to Trouble Diagnosis Procedure for Air Mix Door Motor

Refer to Diagnosis Procedure.

Air mix door motor does not operate normally.

Intake door does not change.

Go to Trouble Diagnosis Procedure for Intake Door Motor

Refer to Diagnosis Procedure.

Intake door motor does not operate normally.

Blower motor operation is malfunctioning.

Go to Trouble Diagnosis Procedure for Blower Motor.

Refer to Diagnosis Procedure.

Magnet clutch does not engage.

Go to Trouble Diagnosis Procedure for Magnet Clutch.

Refer to Diagnosis Procedure.

Insufficient cooling

Go to Trouble Diagnosis Procedure for Insufficient Cooling.

Refer to Component Function Check.

Insufficient heating

Go to Trouble Diagnosis Procedure for Insufficient Heating.

Refer to Component Function Check.

Noise

Go to Trouble Diagnosis Procedure for Noise.

Refer to Symptom Table.

Insufficient Cooling

Component Function Check

Component Function Check

SYMPTOM: Insufficient cooling

INSPECTION FLOW

  1. CONFIRM SYMPTOM BY PERFORMING OPERATION CHECK - TEMPERATURE DECREASE

      1. Press the A/C switch.

      2. Turn temperature control dial counterclockwise to maximum cold.

      3. Check for cold air at discharge air outlets.

    Can a symptom be duplicated?

    YES>>

    GO TO 3.

    NO>>

    GO TO 2.

  2. CHECK FOR ANY SYMPTOMS

    1. Perform a complete operational check and check for any symptoms. Refer to Work Procedure.

    Does another symptom exist?

    YES>>

    Refer to Symptom Table.

    NO>>

    System OK.

  3. CHECK FOR SERVICE BULLETINS

    1. Check for any service bulletins.

    >>

    GO TO 4.

  4. CHECK DRIVE BELTS

    1. Check A/C compressor belt tension. Refer to Inspection.

    Is the inspection result normal?

    YES>>

    GO TO 5.

    NO>>

    Replace A/C compressor belt. Refer to Removal and Installation.

  5. CHECK AIR MIX DOOR MOTOR OPERATION

    1. Check and verify air mix door mechanism for smooth operation.

    Does air mix door operate correctly?

    YES>>

    GO TO 6.

    NO>>

    Check air mix door motor circuit. Refer to Diagnosis Procedure.

  6. CHECK COOLING FAN MOTOR OPERATION

    1. Check and verify cooling fan motor for smooth operation.

    Does cooling fan motor operation correctly?

    YES>>

    GO TO 7.

    NO>>

    Check cooling fan motor. Refer to Component Function Check.

  7. CHECK RECOVERY/RECYCLING EQUIPMENT BEFORE USAGE

    1. Check recovery/recycling equipment before connecting to Nissan Sentra vehicle. Verify there is no pressure in the recovery/recycling equipment by checking the gauges. If pressure exists, recover refrigerant from equipment lines.

    >>

    GO TO 8.

  8. CHECK REFRIGERANT PURITY

      1. Connect recovery/recycling equipment to Nissan Sentra vehicle.

      2. Confirm refrigerant purity in supply tank using recovery/recycling and refrigerant identifier.

    Is the inspection result normal?

    YES>>

    GO TO 9.

    NO>>

    Check contaminated refrigerant. Refer to Description.

  9. CHECK REFRIGERANT PRESSURE

    1. Check refrigerant pressure with manifold gauge connected. Refer to Inspection.

    Is the inspection result normal?

    YES>>

    Perform diagnostic work flow. Refer to Workflow.

    NO>>

    GO TO 10.

  10. CHECK FOR EVAPORATOR FREEZE UP

    1. Start engine and run A/C. Check for evaporator freeze up.

    Does evaporator freeze up?

    YES>>

    Perform diagnostic work flow. Refer Workflow.

    NO>>

    GO TO 11.

  11. CHECK AIR DUCTS

    1. Check ducts for air leaks.

    Is the inspection result normal?

    YES>>

    System OK.

    NO>>

    Repair air leaks.

Insufficient Heating

Component Function Check

Component Function Check

SYMPTOM: Insufficient heating

INSPECTION FLOW

  1. CONFIRM SYMPTOM BY PERFORMING OPERATION CHECK - TEMPERATURE INCREASE

      1. Turn temperature control dial clockwise to maximum heat.

      2. Check for hot air at discharge air outlets.

    Can a symptom be duplicated?

    YES>>

    GO TO 3.

    NO>>

    GO TO 2.

  2. CHECK FOR ANY SYMPTOMS

    1. Perform a complete operational check and check for any symptoms. Refer to Work Procedure.

    Does another symptom exist?

    YES>>

    Refer to Symptom Table.

    NO>>

    System OK.

  3. CHECK FOR SERVICE BULLETINS

    1. Check for any service bulletins.

    >>

    GO TO 4.

  4. CHECK ENGINE COOLING SYSTEM

      1. Check for proper engine coolant level. Refer to Inspection.

      2. Check hoses for leaks or kinks.

      3. Check radiator cap. Refer to Inspection.

      4. Check for air in cooling system.

    >>

    GO TO 5.

  5. CHECK AIR MIX DOOR MOTOR OPERATION

    1. Check and verify air mix door mechanism for smooth operation.

    Does air mix door operate correctly?

    YES>>

    GO TO 6.

    NO>>

    Check the air mix door motor circuit. Refer to Diagnosis Procedure.

  6. CHECK AIR DUCTS

    1. Check for disconnected or leaking air ducts.

    Is the inspection result normal?

    YES>>

    GO TO 7.

    NO>>

    Repair all disconnected or leaking air ducts.

  7. CHECK HEATER HOSE TEMPERATURES

      1. Start engine and warm it up to normal operating temperature.

      2. Touch both the inlet and outlet heater hoses. The inlet hose should be hot and the outlet hose should be warm.

    Is the inspection result normal?

    YES>>

    GO TO 8.

    NO>>

    Both hoses warm: GO TO 9.

  8. CHECK ENGINE COOLANT SYSTEM

    1. Check thermostat operation. Refer to Inspection.

    Is the inspection result normal?

    YES>>

    System OK.

    NO>>

    Repair or replace as necessary.

  9. CHECK HEATER HOSES

    1. Check heater hoses for proper installation.

    Is the inspection result normal?

    YES>>

    System OK.

    NO>>

    1. Back flush heater core.

    2. Drain the water from the system.

    3. Refill system with new engine coolant. Refer to Refilling.

    4. To retest: GO TO 10.

  10. CHECK HEATER HOSE TEMPERATURES

      1. Start engine and warm up to normal operating temperature.

      2. Touch both the inlet and outlet heater hoses. The inlet hose should be hot and the outlet hose should be warm

    Is the inspection result normal?

    YES>>

    System OK.

    NO>>

    Replace heater core. 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.

  1. 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.

  2. CHECK REFRIGERANT PRESSURE SENSOR

    1. Check refrigerant pressure sensor. Refer to Component Function Check.

    Is the inspection result normal?

    YES >>

    GO TO 3.

    NO >>

    Repair or replace malfunctioning parts.

  3. CHECK A/C AMP. OUTPUT SIGNAL

    1. CONSULT

      Select “FAN ON” and “AIR COND SW” in “Data Monitor” mode of “BCM”.

      Monitor item

      Condition

      Status

      AIR COND SW

      A/C switch

      ON

      On

      OFF

      Off

      FAN ON

      Blower motor

      ON

      On

      OFF

      Off

    Is the inspection result normal?

    YES >>

    GO TO 4.

    NO >>

    Replace A/C switch assembly. Refer to Removal and Installation.

  4. CHECK ECM INPUT SIGNAL

    1. 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

      OFF

      Off

      HEATER FAN SW

      Blower motor

      ON

      On

      OFF

      Off

    Is the inspection result normal?

    YES >>

    GO TO 5.

    NO >>

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

  5. CHECK IPDM E/R INPUT SIGNAL

    1. CONSULT

      1. Start engine.

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

        Monitor item

        Condition

        Status

        Compressor request 1

        A/C switch

        ON

        On

        OFF

        Off

    Is the inspection result normal?

    YES >>

    Inspection End.

    NO >>

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

    Ecv (electrical Control Valve)
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    Removal and Installation
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    Other materials:

    U2140-87 Can Comm Err (ecm)
    Dtc Description DTC Description DESCRIPTION CAN (Controller Area Network) is a serial communication line for real time applications. It is an on-Nissan Sentra vehicle multiplex communication line with high data communication speed and excellent error detection ability. Modern Nissan ...

    B24d4-08 A/c Control Comm
    Dtc Description DTC Description DTC DETECTION LOGIC DTC No. CONSULT screen terms (Trouble diagnosis content) DTC detection condition ...

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