Inspection Procedure 4

INSPECTION PROCEDURE 4: When the A/C is Operating, Temperature Inside the Passenger Compartment does not Decrease (Cool Air is not Emitted).

A/C Compressor Sensor Circuit (Part 1):

A/C Compressor Sensor Circuit (Part 2):

TECHNICAL DESCRIPTION (COMMENT)
If cool air is not distributed when the A/C switch is on, the A/C compressor clutch relay system may be defective.

TROUBLESHOOTING HINTS
- Improper amount of refrigerant
- Malfunction of the air thermo sensor
- Malfunction of the ambient air temperature sensor
- Malfunction of the A/C pressure sensor
- Malfunction of the A/C compressor clutch relay
- Malfunction of the A/C refrigerant temperature switch
- Malfunction of the air conditioning compressor clutch
- Malfunction of the A/C-ECU
- Malfunction of the PCM
- Damaged harness wires or connectors

DIAGNOSIS

Required Special Tools:
- MB991223: Test Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (M.U.T-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T-III USB Cable
- MB991910: M.U.T-III Main Harness A (Vehicles with CAN communication system)

STEP 1. Check the defogger and outside/inside air selection damper control motor operation.

Q: Do the defogger and outside/inside air selection damper control motor work normally?

YES : Go to Step 2.

NO : Refer to Inspection procedure 10, "Malfunction of the A/C-ECU power supply system". Inspection Procedure 10

STEP 2. Check the blower motor operation.

Q: Does the blower motor work normally?

YES : Go to Step 3.

NO : Refer to Inspection procedure 5, "Front blower fan and motor do not turn". Inspection Procedure 5

STEP 3. Check the A/C compressor.0

Check the A/C compressor for compressor oil leaks.

Q: Is the check result satisfactory?

YES : Go to Step 4.

NO : Replace the A/C compressor or the expansion valve.

STEP 4. Using scan tool MB991958, read the diagnostic trouble code.






Check if an A/C-ECU DTC is set.

1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the check result satisfactory?

YES : Go to Step 5.

NO : Refer to Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions

STEP 5. Check A/C compressor clutch relay connector B-16X for loose, corroded or damaged terminals, or terminals pushed back in the connector.






Q: Is A/C compressor clutch relay connector B-16X in good condition?

YES : Go to Step 6.

NO : Repair or replace the connector. Check that the air conditioning works normally.

STEP 6. Check the A/C compressor clutch relay continuity.






Follow the table below to check the A/C compressor clutch relay for continuity.






Q: Is the A/C compressor clutch relay in good condition?

YES : Go to Step 7.

NO : Replace the A/C compressor clutch relay. Check that the air conditioning works normally.

STEP 7. Check powertrain control module connector B-20 and A/C compressor assembly B-114 for loose, corroded or damaged terminals, or terminals pushed back in the connector.









Q: Are powertrain control module connector B-20 and A/C compressor assembly B-114 in good condition?

YES : Go to Step 8.

NO : Repair or replace the connector. Check that the air conditioning works normally.

STEP 8. Measure the voltage at A/C compressor assembly connector B-114.






1. Disconnect A/C compressor assembly connector B-114 and measure the voltage at the relay box side.









2. Disconnect powertrain control module connector B-20 and ground harness side terminal No.81.
3. Turn the ignition switch to the "ON" position.






4. A/C compressor assembly connector B-114 terminal 1 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).

Q: Is the measured voltage approx. 12 volts?

YES : Go to Step 15.

NO : Go to Step 9.

STEP 9. Measure the voltage at A/C compressor clutch relay connector B-16X.

CAUTION: The top and bottom of the A/C compressor connector are difficult to identify. Prior to inspection, confirm the triangle mark on the relay box.






1. Disconnect A/C compressor connector B-16X and measure the voltage at the relay box side.
2. Turn the ignition switch to the "ON" position.






3. Measure the voltage between terminal 2 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).

Q: Is the measured voltage approx. 12 volts?

YES : Go to Step 11.

NO: Go to Step 10.

STEP 10. Check the wiring harness between A/C compressor clutch relay connector B-16X (terminal 2) and the ignition switch (IG2).















NOTE: Also check intermediate connector A-13, joint connector C-04, junction block connectors C-214 and C-215 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector A-13, joint connector C-04, junction block connector C-214 or C-215 is damaged, repair or replace the connector.
- Check the A/C compressor clutch relay power supply line for open circuit.

Q: Is the wiring harness between A/C compressor clutch relay connector B-16X (terminal 2) and the ignition switch (IG2) in good condition?

YES : It can be assumed that this malfunction is intermittent.

NO : Repair the wiring harness. Check that the air conditioning works normally.

STEP 11. Measure the voltage at A/C compressor clutch relay connector B-16X.

CAUTION: The top and bottom of the A/C compressor clutch relay connector are difficult to identify. Prior to inspection, confirm the triangle mark on the relay box.






1. Disconnect A/C compressor clutch relay connector B-16X and measure the voltage at the wiring harness side.






2. Measure the voltage between terminal 1 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).

Q: Is the measured voltage approx. 12 volts?

YES : Go to Step 13.

NO: Go to Step 12.

STEP 12. Check the wiring harness between A/C compressor clutch relay connector B-16X (terminal 1) and the battery.









NOTE: Also check intermediate connector A-13 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector A-13 is damaged, repair or replace the connector.
- Check the A/C compressor clutch relay power supply line for open circuit.

Q: Is the wiring harness between A/C compressor clutch relay connector B-16X (terminal 1) and the battery in good condition?

YES : It can be assumed that this malfunction is intermittent.

NO : Repair the wiring harness. Check that the air conditioning works normally.

STEP 13. Check the wiring harness between A/C compressor clutch relay connector B-16X (terminal 4) and A/C compressor connector B-114 (terminal 1).
- Check the A/C compressor clutch relay power supply line for open circuit.









Q: Is the wiring harness between A/C compressor clutch relay connector B-16X (terminal 4) and A/C compressor connector B-114 (terminal 1) in good condition?

YES: Go to Step 14.

NO : Repair the wiring harness. Check that the air conditioning works normally.

STEP 14. Check the wiring harness between powertrain control module connector B-20 (terminal 81) and A/C compressor clutch relay connector B-16X (terminal 3).
- Check the A/C compressor clutch relay power supply line for open circuit.









Q: Is the wiring harness between powertrain control module connector B-20 (terminal 81) and A/C compressor clutch relay connector B-16X (terminal 3) in good condition?

YES : It can be assumed that this malfunction is intermittent.

NO : Repair the wiring harness. Check that the air conditioning works normally.

STEP 15. Check A/C-ECU connector C-43 for loose, corroded or damaged terminals, or terminals pushed back in the connector.






Q: Is A/C-ECU connector C-43 in good condition?

YES : Go to Step 16.

NO : Repair or replace the connector. Check that the air conditioning works normally.

STEP 16. Measure the voltage at A/C-ECU connector C-43.






1. Disconnect A/C-ECU connector C-43 and measure the voltage at the relay box side.









2. Disconnect powertrain control module connector B-20 and ground harness side terminal No.81.
3. Turn the ignition switch to the "ON" position.






4. Measure the voltage between A/C-ECU connector C-43 terminal No.23 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).

Q: Does the measured voltage correspond with this range?

YES : Go to Step 18.

NO: Go to Step 17.

STEP 17. Check the wiring harness between A/C compressor clutch relay connector B-16X (terminal 4) and A/C-ECU connector C-43 (terminal 23).















NOTE: Also check intermediate connectors A-13 and C-24 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector A-13 or C-24 is damaged, repair or replace the connector.
- Check the A/C compressor clutch relay power supply line for open circuit.

Q: Is the wiring harness between A/C compressor clutch relay connector B-16X (terminal 4) and A/C-ECU connector C-43 (terminal 23) in good condition?

YES : It can be assumed that this malfunction is intermittent.

NO : Repair the wiring harness. Check that the air conditioning works normally.

STEP 18. Check the refrigerant temperature switch.

CAUTION: Do not heat more than necessary.






1. Dip the metal part of the refrigerant temperature switch into engine oil and increase the oil temperature using a gas burner or similar.






2. When the oil temperature reaches the standard value, check that voltage is supplied between the terminals.






NOTE: When the oil temperature is 155 °C (311 °F) or more and there is no continuity, the resistance will not be 2Q or lower until the oil temperature reduces to 125 °C (257 °F) or less.

Q: Is the refrigerant temperature switch operating properly?

YES : Go to Step 19.

NO : Replace the refrigerant temperature switch. Check that the air conditioning works normally.

STEP 19. Check the air conditioning compressor clutch operation.






Connect the compressor connector terminal to the battery positive (+) terminal and ground the battery's negative (-) terminal to the compressor unit. At that time, the air conditioning compressor clutch should make a definite operating sound.

Q: Can the sound (click) of the air conditioning compressor clutch operation be heard?

YES : Go to Step 20.

NO : Replace the compressor magnet clutch. Check that the air conditioning works normally.

STEP 20. Check the air thermo sensor.






Measure the resistance between connector terminals 1 and 2 under at least two different temperatures. The resistance values should generally match those in the graph.

NOTE: The temperature at the check should not exceed the range in the graph.

Q: Is the air thermo sensor in good condition?

YES: Go to Step 21.

NO : Replace the air thermo sensor. Check that the air conditioning works normally.

STEP 21. Check the ambient air temperature sensor.






Measure the resistance between the sensor terminals under at least two temperatures. The resistance values should meet the values shown.

NOTE: The temperature should be within the shown range.

Q: Is the ambient air temperature sensor in good condition?

YES : Go to Step 22.

NO : Replace the ambient air temperature sensor. Check that the air conditioning works normally.

STEP 22. Check the A/C pressure sensor operation.

1. Assemble a gauge manifold on the high pressure service valve.









2. Disconnect the A/C pressure sensor connector and connect special tool test harness MB991658 as shown in the illustration.
3. Turn ON the engine and then turn ON the air conditioner switch.






4. At this time, check to see that the voltage of A/C pressure sensor terminal No.2 reflects the specifications of the figure.

NOTE: The allowance shall be defined as ±5%.

Q: Is the A/C pressure sensor operating properly?

YES : Go to Step 23.

NO : Replace the A/C pressure sensor. Check that the air conditioning works normally.

STEP 23. Check the refrigerant level.

Use the refrigerant recovery station to remove all of the refrigerant, and then calculate the amount of the refrigerant and charge it.

Q: Is the refrigerant level correct?

YES : Go to Step 24.

NO : Correct the refrigerant level. Check that the air conditioning works normally.

STEP 24. Replace the A/C-ECU.

Q: Does the A/C operate normally?

YES : No action is necessary and testing is complete.

NO : Replace the powertrain control module. Check that the air conditioning works normally.