Inspection Procedure 5

INSPECTION PROCEDURE 5: A/C outlet air temperature does not increase [Vehicles without A/C]

Air Mixing Damper Control Motor Circuit (Part 1):

Air Mixing Damper Control Motor Circuit (Part 2):

CIRCUIT OPERATION
If the air outlet temperature cannot be adjusted, the air mixing damper control motor circuit may be failed.

TROUBLESHOOTING HINTS
- Malfunction of the air mixing damper control motor
- Malfunction of the heater control unit
- Damaged harness wires or connectors

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe
- 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, check for diagnostic trouble code.







Check if an heater control unit 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 DIAGNOSTIC TROUBLE CODE CHART. Diagnostic Trouble Code Descriptions

NO : Go to Step 2.

STEP 2. Check air mixing damper control motor connector C-118 and heater control unit connector C-47 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Are air mixing damper control motor connector C-118 and heater control unit connector C-47 in good condition?

YES : Go to Step 3.

NO : Repair or replace the connector. Check that the A/C works normally.

STEP 3. Check the wiring harness between heater control unit connector C-47 (terminal 29, 35, 36, 34 and 28) and air mixing damper control motor connector C-118 (terminals 3, 2, 5. 4 and 1).

- Check the heater control unit signal line for open or short circuit.

Q: Are the wiring harness between heater control unit connector C-47 (terminal 29, 35, 36, 34 and 28) and air mixing damper control motor connector C-118 (terminals 3, 2, 5. 4 and 1) in good condition?

YES : Go to Step 4.

NO : Repair the wiring harness. Check that the A/C works normally.

STEP 4. Replace the air mixing damper control motor and check the trouble symptom again

Check the trouble symptom again.

Q: Is the check result satisfactory?

YES : The procedure is complete.

NO : Replace the heater control unit.