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INSPECTION PROCEDURE 10: The blower air volume cannot be changed / Cannot strengthen quantity of the blower air
 
 
 
 
 
 
TECHNICAL DESCRIPTION (COMMENT)
If air volume cannot be adjusted by using the blower control, the A/C control panel, the A/C controller assembly (A/C-ECU) may be faulty.
 
 
 
TROUBLESHOOTING HINT
  • Damaged wiring harness or connectors
  • Malfunction of the A/C controller assembly (A/C-ECU)
  • Adhesion of foreign materials to the blower motor heat sink
  • The A/C air flow passage is clogged
 
 
 
DIAGNOSIS
Required Special Tool:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Check the blower motor power supply circuit (connector, ground terminal).
Check that the blower motor connector C-249, blower relay connector C-402 are connected securely and that the ground terminal is not floating.
Is the check result normal?
Go to Step 2.
Repair or replace the or connector(s) or ground terminal.
 
STEP 2. Check the blower motor.
cautionDo not use parts cleaner to remove the foreign materials adhered to the blower motor fin (heat sink) because the cooling grease applied to the connection of the blower motor and the blower motor fin (heat sink) may be removed.
Remove the blower motor, and check the blower motor fin (heat sink) for adhesion of foreign materials.
Is the check result normal?
Go to Step 3.
Remove the foreign materials.
 
STEP 3. Check the front deck, inside/outside air introduction passage, clean air filter and blower case for foreign materials.
Is the check result normal?
Go to Step 4.
Repair or replace it.
 
STEP 4. M.U.T.-III data list
(1) Continue the following condition more than 20 minutes.
  • Air conditioning switch: OFF
  • Blower knob: Maximum air volume
  • Air outlets: FACE
(2) Check the following data list display contents are normal.
Item No.165: Blower motor high temperature protection
Item No.166: Blower motor overcurrent protection
OK: OFF
Is the check result normal?
Go to Step 6.
Replace the blower motor. Then go to Step 5.
 
STEP 5. Recheck the trouble symptom.
Is the check result normal?
This diagnosis is complete.
Replace the A/C controller assembly (A/C-ECU).
 
STEP 6. Recheck the trouble symptom.
Is the check result normal?
The motor speed is temporarily limited by protection control. This is not a malfunction.
Go to Step 7.
 
STEP 7. M.U.T.-III data list
(1) Continue the following condition.
  • Engine: Operation
  • Blower knob: Maximum air volume
  • Temperature control dial: MAX COOL
  • Air outlets: FACE
(2) Check the following data list display contents are normal.
Item No.168: Blower motor duty ratio (Target)
OK: 64.1 ± 2 %
Is the check result normal?
Replace the blower motor.
Replace the A/C controller assembly (A/C-ECU).