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INSPECTION PROCEDURE 5: The blower air volume cannot be changed <Vehicles with power transistor>
 
 
 
 
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) or the power transistor may be faulty.
 
 
 
TROUBLESHOOTING HINT
  • Malfunction of the power transistor
  • Damaged wiring harness or connectors
  • Malfunction of the A/C controller assembly (A/C-ECU)
 
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. M.U.T.-IIISE diagnostic trouble code
Check that the diagnostic trouble code related to the air conditioning is not set.
Is the DTC set?
Carry out the DTC procedures. Refer to .
Go to Step 2.
 
STEP 2. Resistance measurement at the power transistor connector.
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Continuity between ground terminal and body ground.
OK: Continuity exists (2 Ω or less)
Is the check result normal?
Go to Step 3.
Repair the wiring harness wires between power transistor connector ground terminal and body ground.
 
STEP 3. Check of open circuit in P/TB and P/TC line between blower motor connector, power transistor connector and A/C controller assembly (A/C-ECU) connector.
Is the check result normal?
Go to Step 4.
Repair the connector(s) or wiring harness.
 
STEP 4. Recheck the trouble symptom.
Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Replace the power transistor. 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).