Mazda 6. Manual - part 390

U–64

TROUBLESHOOTING 

FOREWORD

A6E858001038W01

• The areas for inspection (steps) are given according to various circuit malfunctions. Use the following chart to 

verify the symptoms of the trouble in order to diagnose the appropriate area.

End Of Sie

TROUBLESHOOTING INDEX

A6E858001038W02

End Of Sie

TROUBLESHOOTING

No.

TROUBLESHOOTING ITEM

DESCRIPTION

1

Insufficient air (or no air) blown from vents.

• Problem with each vent and/or duct.

2

Amount of air blown from vents does not change. (Full-
auto air conditioner)

• Malfunction in blower system.

3

Amount of air blown from vents does not change. (Manual 
air conditioner)

• Malfunction in blower system.

4

Air intake mode does not change.

• Air intake mode does not change when switching 

REC/FRESH mode.

5

No temperature control with climate control unit.

• Malfunction in A/C unit and/or climate control unit 

air mix system.

6

Windshield fogged.

• A/C compressor does not operate while airflow 

mode is in DEFROSTER or HEAT/DEF modes.

• Air intake mode does not change to FRESH while 

airflow mode is in DEFROSTER or HEAT/DEF 
modes.

7

Air from vents not cold enough.

• Magnetic clutch operates but A/C system 

malfunctions.

8

No cool air.

• Magnetic clutch does not operate.

9

Noise while operating A/C system.

• Noise from magnetic clutch, A/C compressor, hose 

or refrigerant line.

TROUBLESHOOTING 

U–65

U

NO.1 INSUFFICIENT AIR (OR NO AIR) BLOWN FROM VENTS

A6E858001038W03

Diagnostic procedure

End Of Sie

NO.2 AMOUNT OF AIR BLOWN FROM VENTS DOES NOT CHANGE

A6E858001038W04

Full-auto Air Conditioner

• When performing an asterisked (*) troubleshooting inspection, shake the wiring harness and connectors while 

performing the inspection to discover whether poor contact points are the cause of any intermittent 
malfunctions. If there is a problem, check to make sure connectors, terminals and wiring harnesses are 
connected correctly and undamaged.

Diagnostic procedure

1

Insufficient air (or no air) blown from vents.

DESCRIPTION

• Problem with each vent and/or duct.

POSSIBLE 

CAUSE

• Malfunction in VENT mode system (Steps 1—4)

• Malfunction in HEAT mode system (Step 5)

• Malfunction in DEFROSTER mode system (Steps 6—8)

STEP

INSPECTION

ACTION

1

INSPECT TO SEE WHETHER MALFUNCTION 
IS IN VENT MODE OR OTHER MODES

• Does air blow out when in VENT mode?

Yes

Go to Step 4.

No

Go to next step.

2

INSPECT VENT

• Is vent clogged?

Yes

Remove obstruction, then go to Step 8.

No

Go to next step.

3

VERIFY THAT DUCT IN DASHBOARD IS 
INSTALLED

• Is duct in dashboard properly installed?

Yes

Inspect duct for clogging, deformity and air leakage, then go 
to Step 8.

No

Install duct securely in the proper position, then go to Step 
8.

4

INSPECT TO SEE WHETHER MALFUNCTION 
IS IN HEAT MODE OR DEFROSTER MODE

• Does air blow out when in HEAT mode?

Yes

Go to next step.

No

Inspect vent for clogging, then go to Step 8.

5

INSPECT DEFROSTER MODE

• Does air blow out when in DEFROSTER 

mode?

Yes

Operation is okay. Recheck malfunction symptoms.

No

Go to next step.

6

INSPECT VENT

• Is vent clogged?

Yes

Remove obstruction, then go to Step 8.

No

Go to next step.

7

VERIFY THAT DEFROSTER DUCT IS 
INSTALLED

• Is defroster duct properly installed?

Yes

Inspect duct for clogging, deformity, and air leakage, then 
go to next step.

No

Install duct securely in proper position, then go to next step.

8

CONFIRM THAT MALFUNCTION SYMPTOMS 
DO NOT RECUR AFTER REPAIR

• Does air blow out?

Yes

Troubleshooting completed.
Explain repairs to customer.

No

Recheck malfunction symptoms, then repeat from Step 1 if 
malfunction recurs.

2

Amount of air blown from vents does not change.

DESCRIPTION

• Malfunction in blower system.

POSSIBLE 

CAUSE

• Malfunction in blower unit (Steps 3, 4, 12)

• Malfunction in blower motor (Steps 5—9)

• Malfunction in power MOS FET system (Steps 10, 11, 13, 14)

• Malfunction in climate control unit (Step 15)

STEP

INSPECTION

ACTION

1

INSPECT BLOWER 40 A FUSE

• Inspect BLOWER 40 A fuse.

• Is it okay?

Yes

Go to next step.

No

Replace fuse, then go to Step 15. If fuse burns out 
immediately, go to next step.

2

INSPECT TO SEE WHETHER MALFUNCTION 
IS IN BLOWER UNIT OR ELSEWHERE

• Turn ignition switch to ON position.

• Recirculate air inside vehicle.

• Does blower unit fan rotate smoothly?

Yes

Go to Step 4.

No

Go to next step.

3

INSPECT BLOWER UNIT INTAKE VENT

• Is intake vent of blower unit clogged?

Yes

Remove obstruction, then go to Step 15.

No

Inspect if there are any obstruction in passage between 
blower unit to A/C unit, then go to Step 15.

U–66

TROUBLESHOOTING 

4*

INSPECT TO SEE WHETHER MALFUNCTION 
IS IN BLOWER RELAY SYSTEM OR POWER 
MOS FET SYSTEM

• Turn ignition switch to ON position.

• Test voltage at the following terminal of 

blower motor.
— Terminal B (blower motor operation 

signal)

• Is voltage approximately 12 V?

Yes

Go to Step 8.

No

Go to next step.

5*

INSPECT TO SEE WHETHER MALFUNCTION 
IS IN WIRING HARNESS (LACK OF 
CONTINUITY BETWEEN FUSE BLOCK AND 
BLOWER RELAY) OR ELSEWHERE

• Test voltage at the following terminal of 

blower relay.
— Terminal A (IG2 signal)
— Terminal C (B+ signal)

• Is voltage approximately 12 V?

Yes

Go to next step.

No

Repair wiring harness between blower relay and BLOWER 
40 A fuse, then go to Step 15.

6*

INSPECT TO SEE WHETHER MALFUNCTION 
IS IN WIRING HARNESS (LACK OF 
CONTINUITY BETWEEN BLOWER RELAY 
AND GROUND) OR ELSEWHERE

• Test voltage at the following terminal of 

blower relay.
— Terminal E (GND signal)

• Is voltage approximately 0 V?

Yes

Go to next step.

No

Repair wiring harness between blower relay and ground, 
then go to Step 15.

7*

INSPECT TO SEE WHETHER MALFUNCTION 
IS IN WIRING HARNESS (LACK OF 
CONTINUITY BETWEEN BLOWER RELAY 
AND BLOWER MOTOR) OR BLOWER RELAY

• Test voltage at the following terminal of 

blower relay.
— Terminal D (blower motor operation 

signal)

• Is voltage approximately 12 V?

Yes

Repair wiring harness between blower relay and blower 
motor, then go to Step 15.

No

Replace blower relay, then go to Step 15.

8*

INSPECT TO SEE WHETHER MALFUNCTION 
IS IN BLOWER MOTOR OR ELSEWHERE

• Test voltage at the following terminal of 

blower motor.
— Terminal B (blower motor operation 

signal)

• Is voltage approximately 12 V?

Yes

Go to next step.

No

Inspect blower motor, then go to Step 15.

9*

INSPECT TO SEE WHETHER MALFUNCTION 
IS IN WIRING HARNESS (LACK OF 
CONTINUITY BETWEEN BLOWER MOTOR 
AND POWER MOS FET) OR ELSEWHERE

• Test voltage at the following terminal of 

power MOS FET.
— Terminal C (blower motor operation 

signal)

• Is voltage approximately 12 V?

Yes

Go to next step.

No

Repair wiring harness between blower motor and power 
MOS FET, then go to Step 15.

10*

INSPECT TO SEE WHETHER MALFUNCTION 
IS IN WIRING HARNESS (LACK OF 
CONTINUITY BETWEEN POWER MOS FET 
AND GROUND) OR ELSEWHERE

• Test voltage at the following terminal of 

power MOS FET.
— Terminal A (blower motor operation 

signal)

• Is voltage approximately 0 V?

Yes

Go to next step.

No

Repair wiring harness between power MOS FET and 
ground, then go to Step 15.

11

INSPECT BLOWER UNIT

• Inspect fan in blower unit.

— Is fan free of interference with blower unit 

case?

— Is fan free of foreign material and 

obstruction?

• Is fan okay?

Yes

Go to next step.

No

Remove obstruction, repair or replace fan and blower unit 
case, then go to Step 15.

STEP

INSPECTION

ACTION

TROUBLESHOOTING 

U–67

U

End Of Sie

NO.3 AMOUNT OF AIR BLOWN FROM VENTS DOES NOT CHANGE

A6E858001038W05

Manual Air Conditioner

Diagnostic procedure

12*

INSPECT TO SEE WHETHER MALFUNCTION 
IS IN POWER MOS FET OR ELSEWHERE

• Disconnect power MOS FET connector.

• Test voltage at the following terminal of 

power MOS FET.
— Terminal B (blower motor control signal)

• Is voltage approximately 10 V?

Yes

Replace power MOS FET, then go to Step 15.

No

Go to next step.

13*

INSPECT TO SEE WHETHER MALFUNCTION 
IS IN WIRING HARNESS (LACK OF 
CONTINUITY BETWEEN POWER MOS FET 
AND CLIMATE CONTROL UNIT) OR 
ELSEWHERE

• Turn ignition switch to LOCK position.

• Disconnect climate control unit connector.

• Inspect for continuity at the following 

terminals between power MOS FET and 
climate control unit.
— Terminal B—1C (24-pin, blower motor 

control signal)

— Terminal C—1A (24-pin, blower motor 

feedback signal)

• Is there continuity?

Yes

Go to next step.

No

Repair wiring harness between power MOS FET and 
climate control unit, then go to Step 15.

14*

INSPECT TO SEE WHETHER MALFUNCTION 
IS IN CLIMATE CONTROL UNIT OR WIRING 
HARNESS (SHORT TO GROUND BETWEEN 
POWER MOS FET AND CLIMATE CONTROL 
UNIT)

• Inspect for continuity at the following terminal 

between power MOS FET and ground.
— Terminal B (blower motor control signal)—

ground

• Is there continuity?

Yes

Repair wiring harness between power MOS FET and 
ground, then go to next step.

No

Replace climate control unit, then go to next step.

15

CONFIRM THAT MALFUNCTION SYMPTOMS 
DO NOT RECUR AFTER REPAIR

• Is air discharged from vent?

Yes

Troubleshooting completed.
Explain repairs to customer.

No

Recheck malfunction symptoms, then repeat from Step 1 if 
malfunction recurs.

STEP

INSPECTION

ACTION

3

Amount of air blown from vents does not change.

DESCRIPTION

• Malfunction in blower system.

POSSIBLE 

CAUSE

• Blower relay, blower motor, resistor, fan switch malfunction (Step 1)

• Blower unit malfunction (Steps 2—4)

STEP

INSPECTION

ACTION

1

INSPECT BLOWER SYSTEM

• Inspect the following systems and electrical 

parts.
— Blower relay
— Blower motor
— Resistor
— Fan switch
— Related wiring harnesses

• Are they okay?

Yes

Go to next step.

No

Repair or replace malfunctioning part, then go to Step 5.

2

CHECK TO SEE WHETHER MALFUNCTION 
IS IN BLOWER UNIT OR ELSEWHERE

• Turn ignition switch to ON position.

• Turn fan switch on.

• Recirculate air inside vehicle.

• Does fan in blower unit rotate smoothly?

Yes

Go to Step 4.

No

Go to next step.