Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Nissan Altima. However, it is still accessible from the selected car via links, so may be relevant.

Symptom:

Magnet clutch does not engage when A/C switch and fan switch are ON.

CHECK POWER SUPPLY FOR COMPRESSOR
Disconnect compressor harness connector.

Fig 1: Compressor Volage Table
Courtesy of NISSAN MOTOR CO., U.S.A.

Fig 2: Checking Power Supply For Compressor
Courtesy of NISSAN MOTOR CO., U.S.A.

OK or NG
1. OK: GO TO 2.
2. NG: GO TO 3.
CHECK MAGNET CLUTCH COIL
check magnet clutch coil.

OK or NG
1. OK: Check compressor mounting points for looseness or corrosion and repair as necessary.
2. NG: Replace magnet clutch. Refer to "REMOVAL AND INSTALLATION FOR COMPRESSOR CLUTCH ".
CHECK MAGNET CLUTCH COIL POWER SUPPLY FROM IPDM E/R
Reconnect compressor harness connector.

Fig 3: Magnet Clutch Coil Voltage Table
Courtesy of NISSAN MOTOR CO., U.S.A.

Fig 4: Checking Magnet Clutch Coil Power Supply From IPDM E/R
Courtesy of NISSAN MOTOR CO., U.S.A.

OK or NG
1. OK: Repair harness or connector between IPDM E/R and compressor.
2. NG: GO TO 4.
CHECK INTAKE SENSOR CIRCUIT
Refer to "INTAKE SENSOR CIRCUIT ".

OK or NG
1. OK: GO TO 5.
2. NG: Repair as necessary.
CHECK REFRIGERANT PRESSURE SENSOR
Refer to "ALTIMA 2.5L " for (QR2DE models) or "ALTIMA 3.5L " for (VQ35DE models).

OK or NG
1. OK: GO TO 6.
2. NG: Repair as necessary.
CHECK FAN ON SIGNAL TO A/C CONTROL UNIT AND BCM
1. Disconnect A/C control unit harness connector M51.
2. Measure voltage between A/C control unit and body ground.
3. Reconnect A/C control unit harness connector M51 and disconnect BCM harness connector M18.
4. Measure voltage between BCM and body ground.
  
  Fig 5: A/C Control Unit And BCM Voltage Condition Table
  Courtesy of NISSAN MOTOR CO., U.S.A.
  
  Fig 6: Checking Fan On Signal To A/C Control Unit And BCM
  Courtesy of NISSAN MOTOR CO., U.S.A.
OK or NG
1. OK: GO TO 8.
2. NG: GO TO 7.
CHECK FAN SWITCH
check fan switch. Refer to "FAN SWITCH ".

OK or NG
1. OK: Repair harness or connectors between fan switch and A/C control unit and BCM.
2. NG: Replace fan switch.
CHECK COMPRESSOR ON SIGNAL
1. Reconnect A/C control unit harness connector.
2. With fan switch ON, measure voltage between A/C control unit and body ground with A/C switch OFF and ON.
  
  Fig 7: Compressor Voltage Condition Table
  Courtesy of NISSAN MOTOR CO., U.S.A.
  
  Fig 8: Checking Compressor On Signal
  Courtesy of NISSAN MOTOR CO., U.S.A.
OK or NG
1. OK: GO TO 9.
2. NG: Replace A/C control unit.
CHECK COMPRESSOR ON SIGNAL CIRCUIT
1. Disconnect A/C control unit harness connector.
2. Check continuity between A/C control unit and BCM.
  
  Fig 9: Compressor Circuit Continuity Table
  Courtesy of NISSAN MOTOR CO., U.S.A.
  
  Fig 10: Checking Compressor On Signal Circuit
  Courtesy of NISSAN MOTOR CO., U.S.A.
If OK, check harness for short.

OK or NG
1. OK: GO TO 10.
2. NG: Repair harness or connectors.
CHECK CAN COMMUNICATION CIRCUITS
Check CAN communication circuits between BCM to ECM and between ECM to IPDM E/R. Refer to "CAN COMMUNICATION ".

OK or NG
1. OK: ECM is malfunctioning.
2. NG: Repair or replace component base on diagnosis.