Mitsubishi 380. Manual - part 201

AUTO A/C DIAGNOSIS

HEATER, AIR CONDITIONING AND VENTILATION

55-100

STEP 17. Replace the power transistor.

Q: Does the blower motor operate normally?

YES : No action is necessary and testing is complete.
NO :  Replace the A/C-ECU. Check that the air conditioning 

works normally. 

INSPECTION PROCEDURE 6: Front Blower Air Amount cannot be Changed.

.

CIRCUIT OPERATION

If the blower motor speed cannot be changed, the 
power transistor circuit is suspected.

.

TROUBLESHOOTING HINTS

• Malfunction of the power transistor

• Malfunction of the front A/C-ECU

• Damaged harness wires or connectors

• Refer to component locations GROUP-

70

• Refer to configuration diagrams GROUP-

80

• Refer to circuit diagrams GROUP-

90

DIAGNOSIS

Required Special Tool:

• MB991223: Test Harness Set

STEP 1. Check blower power transistor connector C-104 
for loose, corroded or damaged terminals, or terminals 
pushed back in the connector.
Q: Is power transistor connector C-104 in good condition?

YES : Go to Step 2.
NO :  Repair or replace the connector. Refer to GROUP 

00E, Harness Connector Inspection 

P.00E-2

.The 

blower motor should operate normally.

25DB119A

CONNECTORS: C-15, C-104, C-115

C-104

C-115

C-15 (B)

25DB116A

HARNESS SIDE

CONNECTOR: C-104

AUTO A/C DIAGNOSIS

HEATER, AIR CONDITIONING AND VENTILATION

55-101

STEP 2. Measure the resistance at power transistor 
connector C-104.
(1) Disconnect power transistor connector C-104, and measure 

the resistance at the wiring harness side.

(2) Measure the resistance value between terminal 2 and 

ground.

• The measured value should be 2 ohms or less.

Q: Does the measured resistance value correspond with 

this range?
YES :  Go to Step 4.
NO :   Go to Step 3.

STEP 3. Check the wiring harness between power 
transistor connector C-104 (terminal 2) and ground.
Q: Is the wiring harness between power transistor 

connector C-104 (terminal 2) and ground in good 
condition?
YES : The blower motor should operate normally.
NO :  Repair the wiring harness. The blower motor should 

operate normally.

STEP 4. Check blower motor connector C-115 for loose, 
corroded or damaged terminals, or terminals pushed back 
in the connector.
Q: Is blower motor connector C-115 in good condition?

YES : Go to Step 5.
NO :  Repair or replace the connector. Refer to GROUP 

00E, Harness Connector Inspection 

P.00E-2

.The 

blower motor should operate normally.

25DB116A

HARNESS SIDE

CONNECTOR: C-104

AC209364JD

CONNECTOR C-104 
(HARNESS SIDE)

25DB116A

HARNESS SIDE

CONNECTOR: C-104

25DB110A

CONNECTOR: C-115

HARNESS SIDE

AUTO A/C DIAGNOSIS

HEATER, AIR CONDITIONING AND VENTILATION

55-102

STEP 5. Check the wiring harness between power 
transistor connector C-104 (terminal 4) and blower motor 
connector C-115 (terminal 2).
Q: Is the wiring harness between power transistor 

connector C-104 (terminal 4) and blower motor 
connector C-115 (terminal 2) in good condition?
YES :  Go to Step 6.
NO :  Repair the wiring harness. The blower motor should 

operate normally.

STEP 6. Check A/C-ECU connector C-15 for loose, 
corroded or damaged terminals, or terminals pushed back 
in the connector.
Q: Is A/C-ECU connector C-15 in good condition?

YES : Go to Step 7.
NO :  Repair or replace the connector. Refer to GROUP 

00E, Harness Connector Inspection 

P.00E-2

.The 

blower motor should operate normally.

25DB117A

C-104

C-115

HARNESS SIDE

C-104

HARNESS SIDE

C-115

CONNECTORS: C-104, C-115

25DB120A

CONNECTOR: C-15

C-105 (B)

HARNESS SIDE

AUTO A/C DIAGNOSIS

HEATER, AIR CONDITIONING AND VENTILATION

55-103

STEP 7. Check the wiring harness between power 
transistor connector C-104 (terminals 1 and 3) and 
A/C-ECU connector C-15 (terminals 17 and 18).
Q: Are the wiring harness between power transistor 

connector C-104 (terminals 1 and 3) and A/C-ECU 
connector C-15 (terminals 17 and 18) in good condition?
YES :  Go to Step 8.
NO :  Repair the wiring harness. The blower motor should 

operate normally.

STEP 8. Replace the power transistor.

Q: Does the blower motor operate normally?

YES : It can be assumed that this malfunction is intermittent. 

Refer to GROUP 00, How to Use 
Troubleshooting/Inspection Service Points 

− How to 

Cope with Intermittent Malfunctions 

P.00-14

.

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

works normally. 

25DB121A

C-104

HARNESS SIDE

C-104

HARNESS SIDE

C-15

CONNECTORS: C-15, C-104

C-15 (B)