Mitsubishi Galant (2004+). Manual - part 770

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-219

STEP 15. 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 16.
NO :  Repair the wiring harness. The blower motor should 

operate normally.

STEP 16. 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 17.
NO :  Repair the wiring harness. The blower motor should 

operate normally.

AC305234

C-104

C-115

HARNESS SIDE

C-104

HARNESS SIDE

C-115

AR

CONNECTORS: C-104, C-115

AC305234

CONNECTORS: C-15, C-104

HARNESS SIDE

C-15

C-104

HARNESS SIDE

C-104

C-15 (B)

AS

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-220

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.

BLOWER RELAY

FRONT
BLOWER
MOTOR

POWER
TRANSISTOR

A/C-ECU

Blower Motor Circuit

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-221

.

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

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.

AC305233BW

CONNECTORS: C-15, C-104, C-115

C-104

C-115

C-15 (B)

AC305233

HARNESS SIDE

BV

CONNECTOR: C-104

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-222

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.

AC305233

HARNESS SIDE

BV

CONNECTOR: C-104

AC209364JD

CONNECTOR C-104 
(HARNESS SIDE)

AC305233

HARNESS SIDE

BV

CONNECTOR: C-104

AC305233BN

CONNECTOR: C-115

HARNESS SIDE