DTC 32: Potentiometer System of Mode Selection Damper Control Motor Assembly.: Diagnosis

Required Special Tools: 

• MB991223: Harness Set
• MB992006: Extra Fine Probe
• MB991958: Scan Tool (MUT-III Sub Assembly)
  • MB991824: Vehicle Communication Interface (V.C.I.)
  • MB991827: MUT-III USB Cable
  • MB991911: MUT-III Main Harness B (Vehicles without CAN communication system)

1. STEP 1. Using scan tool MB991958, check data list. 
   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.

   Item 32: mode selection damper control motor and potentiometer

   OK: Check that the set position of the heater control matches the displayed position on the scan tool MB991958.

   Q: Does the data list show approximately 0% (at FACE position), approximately 60% (at FOOT position), approximately 80% (at FOOT/DEF position), and approximately 100% (at DEF position)? 

   YES:  It can be assumed that this malfunction is intermittent (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).

   NO:  Go to Step 2.

   Fig 1: Connecting Scan Tool To Data Link Connector

   
2. STEP 2. Check the mode selection damper control motor and potentiometer. 
   CAUTION: Do not apply battery voltage when the damper is in the FACE or DEF position.
   1. Check the mode selection damper control motor by the following procedures.
      LEVER POSITION AND OPERATION REFERENCE
      
      

      LEVER POSITION	BATTERY CONNECTION	LEVER OPERATION
      At the DEF position	Connect terminal 1 to the positive battery terminal Connect terminal 2 to the negative battery terminal	The lever moves from the DEF position to the outside position
      At the FACE position	Connect terminal 2 to the positive battery terminal Connect terminal 1 to the negative battery terminal	The lever moves from the FACE position to the inside position

      Fig 2: Identifying FACE And DEF Position

      
   2. Check the mode selection damper potentiometer: While checking the mode selection damper control motor, measure the resistances between terminal Nos. 3 and 5 as well as terminal Nos. 3 and 7. At this time, the resistances should change gradually within the standard value.

      Standard value: 0.96 - 5.76 kΩ 

   Q: Does mode selection damper potentiometer work normally? 

   YES:  Go to Step 3.

   NO:  Replace the mode selection damper control motor and potentiometer. Then go to  Step 5.

3. STEP 3. Check mode selection damper control motor and potentiometer connector D-22 and A/C-ECU connector D-24 for damage. 

   Q: Is mode selection damper control motor and potentiometer connector D-22 and A/C-ECU connector D-24 in good condition? 

   YES:  Go to Step 4.

   NO:  Repair or replace the connector. Refer to HARNESS CONNECTOR INSPECTION . Then go to  Step 5.

   Fig 3: Identifying Damper Control Motor And Potentiometer Connector D-22 And D-24

   
4. STEP 4. Check the wiring harness between mode selection damper control motor and potentiometer connector D-22 (terminals 7, 3 and 5) and A/C-ECU D-24 (terminals 21, 32 and 29). 

   Q: Is the wiring harness between mode selection damper control motor and potentiometer connector D-22 (terminals 7, 3 and 5) and A/C-ECU D-24 (terminals 21, 2 and 29) in good condition? 

   YES:  Replace the A/C-ECU (Refer to A/C CONTROL PANEL AND A/C CONTROL UNIT  ). Then go to Step 5.

   NO:  Repair the wiring harness. Then go to Step 5.

   Fig 4: Identifying Damper Control Motor And Potentiometer Connector D-22 And D-24

   
5. STEP 5. Recheck for diagnostic trouble code. 

   Q: Is DTC 32 set? 

   YES:  Return to  Step 1.

   NO:  The procedure is complete.