Inspection Procedure 12

When Sunlight Intensity Changes, Air Outlet Temperature Does Not Change.

Photo Sensor Motor Circuit:

CIRCUIT OPERATION
When the blower air temperature cannot be changed even if the preset temperature is changed, the sensors may be defective.

TROUBLESHOOTING HINTS
- Improper amount of refrigerant
- Malfunction of the A/C pressure sensor
- Malfunction of the photo sensor
- Malfunction of the A/C-ECU
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: MUT-III USB Cable
- MB991910: MUT-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 Manual A/C Diagnosis.




STEP 2. Using scan tool MB991958, read diagnostic trouble code.

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. 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 DTC set?

YES: Refer to Trouble Code Descriptions. Diagnostic Trouble Code Descriptions

NO: Go to Step 3.




STEP 3. Using scan tool MB991958, check data list item 06: Photo sensor.

1. Connect scan tool MB991958 to the data link connector.
2. Start the engine.
3. Set scan tool MB991958 to the data reading mode for item 06: Photo sensor.
- Check that the display on the scan tool changes when the photo sensor is covered with hands.

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

Q: Is the sensor within the specified range?

YES: Go to Step 7.

NO: Go to Step 4.







STEP 4. Check A/C-ECU connectors C-15, C-16 and photo sensor connector C-04 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Are A/C-ECU connectors C-15, C-16 and photo sensor connector C-04 in good condition?

YES: Go to Step 5.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. Check that the air conditioning works normally.







STEP 5. Check the wiring harness between photo sensor connector C-04 (terminal 1, 2) and A/C-ECU connector C-15 (terminal 19), C-16 (terminal 25).

Q: Is the wiring harness between photo sensor connector C-04 (terminal 1, 2) and A/C-ECU connector C-15 (terminal 19), C-16 (terminal 25) in good condition?

YES: Go to Step 6.

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

STEP 6. Replace the photo sensor.

Q: Does the A/C operate normally?

YES: No action is necessary and testing is complete.

NO: Replace the A/C-ECU. Check that the air conditioning works normally.

STEP 7. 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: Refer to Symptom Chart.

NO: Correct the refrigerant level (Refer to On-vehicle Service). Check that the air conditioning works normally.