Inspection Procedure 3

INSPECTION PROCEDURE 3: The Compressor does not Work.






































FUNCTION

Compressor that recovers the refrigerant, which evaporated in the evaporator and became a high-temperature and high-pressure gas, and turns it into liquid again.

PROBABLE CAUSES

- Insufficient refrigerant
- Malfunction of connector.
- Malfunction of the harness (A/C compressor circuit is open/shorted to ground)
- Malfunction of the A/C pressure sensor.
- Malfunction of the A/C compressor.
- Malfunction of the A/C compressor clutch relay.
- Malfunction of the A/C-ECU.

DIAGNOSIS

Required Special Tools:

- MB991223: Harness Set
- MB992006: Extra Fine Probe
- MB991658: Test Harness Set
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

STEP 1. Using scan tool MB991958, diagnose the CAN bus line.





CAUTION:
To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

(1)Connect scan tool MB991958 to the data link connector.
(2)Turn the ignition switch to the "ON" position.
(3)Diagnose the CAN bus line.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the CAN bus line found to be normal?

YES Go to Step 2.

NO Repair the CAN bus lines Precautions on How to Repair the CAN Bus Line(s)).

STEP 2. 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 Refer to DIAGNOSTIC TROUBLE CODE CHART Automatic Air Conditioning.
NO Go to Step 3.
STEP 3. Using scan tool MB991958, check data list.

(1)Connect scan tool MB991958 to the data link connector.

(2)Start the engine.

(3)Set scan tool MB991958 to the data reading mode.

- Item 66: Air conditioning switch

NOTE:
Check that the scan tool displays "ON" when the A/C switch is ON.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Does the scan tool display "ON" when the A/C switch is on?

YES Go to Step 5.
NO Go to Step 4.
STEP 4. Retest the system.

Check the trouble symptom again.

Q. Is the check result satisfactory?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.
NO Replace the A/C-ECU.
STEP 5. Check the refrigerant level.

Sight Glass Refrigerant Level Test.

Q. Is the check result satisfactory?

YES Go to Step 6.
NO Replenish the refrigerant Charging [Vehicles Using R-134a Refrigerant]).
STEP 6. Check A/C pressure sensor connector A-34 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q. Is A/C pressure sensor connector A-34 in good condition?

YES Go to Step 7.

NO Repair or replace the connector. Harness Connector Inspection.

STEP 7. 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 A/C 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 8.

NO Replace the A/C pressure sensor.

STEP 8. Check A/C-ECU connector C-15 and C-20 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q. Are A/C-ECU connector C-15 and C-20 in good condition?

YES Go to Step 9.

NO Repair or replace the connector. Harness Connector Inspection.

STEP 9. Check the wiring harness for open circuit.









(1)Disconnect A/C-ECU connector C-15 and A/C pressure sensor connector A-34, and measure the resistance at the wiring harness side.





(2)Measure the resistance between A/C-ECU connector C-15 terminal 12 and A/C pressure sensor connector A-34 terminal 3.
OK: Less than 2 ohms

Q. Is the check result normal?

YES Go to Step 11.

NO Go to Step 10.

STEP 10. Check the wiring harness between A/C-ECU connector C-15 (terminal 12) and A/C pressure sensor connector A-34 (terminal 3).













NOTE:
Also check intermediate connector C-24 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-24 is damaged, repair or replace the connector as described in Harness Connector Inspection Harness Connector Inspection.

Q. Is the wiring harness between A/C-ECU connector C-15 (terminal 12) and A/C pressure sensor connector A-34 (terminal 3) in good condition?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.

NO Repair the wiring harness.

STEP 11. Check the wiring harness for open circuit.









(1)Disconnect A/C-ECU connector C-20 and A/C pressure sensor connector A-34, and measure the resistance at the wiring harness side.





(2)Measure the resistance between A/C-ECU connector C-20 terminal 26 and A/C pressure sensor connector A-34 terminal 2.
OK: Less than 2 ohms

Q. Is the check result normal?

YES Go to Step 13.

NO Go to Step 12.

STEP 12. Check the wiring harness between A/C-ECU connector C-20 (terminal 26) and A/C pressure sensor connector A-34 (terminal 2).













NOTE:
Also check intermediate connector C-24 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-24 is damaged, repair or replace the connector as described in Harness Connector Inspection Harness Connector Inspection.

Q. Is the wiring harness between A/C-ECU connector C-20 (terminal 26) and A/C pressure sensor connector A-34 (terminal 2) in good condition?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.

NO Repair the wiring harness.

STEP 13. Measure the resistance at A/C-ECU connector C-20.





(1)Disconnect A/C-ECU connector C-20, and measure the resistance at the wiring harness side.





(2)Measure the resistance value between terminal 34 and ground.
OK: 1 kohms or more

Q. Does the measured resistance value correspond with this range?

YES Go to Step 15.

NO Go to Step 14.

STEP 14. Check the wiring harness between A/C-ECU connector C-20 (terminal 34) and A/C pressure sensor connector A-34 (terminal 1).













NOTE:
Also check intermediate connector C-24 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-24 is damaged, repair or replace the connector as described in Harness Connector Inspection Harness Connector Inspection.

Q. Is the wiring harness between A/C-ECU connector C-20 (terminal 34) and A/C pressure sensor connector A-34 (terminal 1) in good condition?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.

NO Repair the wiring harness.

STEP 15. Check A/C compressor assembly connector B-27 for loose, corroded or damaged terminals, or terminals pushed back in the connector.









Q. Is A/C compressor assembly connector B-27 in good condition?

YES Go to Step 16.

NO Repair or replace the connector. Harness Connector Inspection.

STEP 16. Check the A/C 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 A/C compressor clutch should make a definite operating sound.

Q. Can the sound (click) of the A/C compressor clutch operation be heard?

YES Go to Step 17.

NO Replace the compressor magnet clutch.

STEP 17. 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 18.

NO Replace the A/C compressor clutch relay.

STEP 18. Check the wiring harness for open circuit.





(1)Disconnect A/C compressor clutch relay connector B-17X, and measure the resistance at the wiring harness side.





(2)Measure the resistance between A/C compressor clutch relay connector B-17X terminal 1 and ground.
OK: Less than 2 ohms

Q. Is the check result normal?

YES Go to Step 20.

NO Go to Step 19.

STEP 19. Check the wiring harness between A/C compressor clutch relay connector B-17X (terminal 1) and the battery.









NOTE:
Also check intermediate connector A-15 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector A-15 is damaged, repair or replace the connector as described in Harness Connector Inspection Harness Connector Inspection.

Q. Is the wiring harness between A/C compressor clutch relay connector B-17X (terminal 1) and the battery in good condition?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.

NO Repair the wiring harness.

STEP 20. Check the wiring harness for open circuit.













(1)Disconnect A/C compressor assembly connector B-27 and A/C compressor clutch relay connector B-17X, and measure the resistance at the wiring harness side.





(2)Measure the resistance between A/C compressor assembly connector B-27 terminal 1 and A/C compressor clutch relay connector B-17X terminal 4.
OK: Less than 2 ohms

Q. Is the check result normal?

YES Go to Step 22.

NO Go to Step 21.

STEP 21. Check the wiring harness between A/C compressor assembly connector B-27 (terminal 1) and A/C compressor clutch relay connector B-17X (terminal 4).













Q. Is the wiring harness between A/C compressor assembly connector B-27 (terminal 1) and A/C compressor clutch relay connector B-17X (terminal 4) in good condition?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.

NO Repair the wiring harness.

STEP 22. Retest the system.

Check that the A/C works normally.

Q. Is the check result satisfactory?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.
NO Replace the A/C-ECU.