Subaru Legacy III (2000-2003 year). Manual - part 885

AC-76

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC) (RHD 

MODEL)

F: DTC 28 OR 29 (MODE DOOR ACTUATOR POTENTIOMETER LINE)

WIRING DIAGRAM:

1

3

5

6

7

E

i45

MODE DOOR

ACTUATOR

3

11

4

1

2

A10

A5

A14

A16

A8

HEATER MODULE

AUTO A/C

CONTROL MODULE

A:  i48

B:  i49

E

1 2 3 4 5 6 7

i48

1 2 3 4 5 6 7 8
9 10 11 12 13 14 15 16

A:

i45

1 2 3

4 5 6

7 8 9 10 11 12 13 14

AC-00377

AC-77

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC) (RHD 

MODEL)

Step

Value

Yes

No

1

CHECK MODE DOOR ACTUATOR.
1) Turn ignition switch to OFF.
2) Remove mode door actuator.
3) Make sure that mode door actuator is oper-

ated when connecting battery positive (+) 
terminal to terminal No. 6 and negative (-) 
terminal to terminal No. 7 of mode door 
actuator.
Does the mode door actuator operate?

Ventilation motor operates.

Go to step 2.

Replace mode 
door actuator.

2

CHECK POTENTIOMETER.
Measure resistance for the power supply line 
of the potentiometer.

Terminals

(E) No. 1 — No. 3:

Is the measured value same as the specified 
value?

Approx. 6.0 k

Ω

Go to step 3.

Replace mode 
door actuator.

3

CHECK POTENTIOMETER.
Measure resistance for the signal line of the 
potentiometer, when the lever is in the FULL 
VENT position.

Terminals

(E) No. 1 — No. 5:

Is the measured value same as the specified 
value?

Approx. 1.2 k

Ω

Go to step 4.

Replace mode 
door actuator.

4

CHECK POTENTIOMETER.
Measure resistance for the signal line of the 
potentiometer, when the lever is in the FULL 
DEF position.

Terminals

(E) No. 1 — No. 5:

Is the measured value same as the specified 
value?

Approx. 4.5 k

Ω

Go to step 5.

Replace mode 
door actuator.

5

CHECK HARNESS CONNECTOR BETWEEN 
A/C CONTROL MODULE AND MODE DOOR 
ACTUATOR.
1) Disconnect connector from A/C control 

module.

2) Measure resistance of harness between A/

C control module and mode door actuator.

Connector & terminal

(i48) No. 14 — (E) No. 5:

Is the measured value less than the speci-
fied value?

1 

Ω

Go to step 6.

Repair harness 
between A/C con-
trol module and 
mode door actua-
tor.

6

CHECK HARNESS CONNECTOR BETWEEN 
A/C CONTROL MODULE AND MODE DOOR 
ACTUATOR.
Measure resistance of harness between A/C 
control module and mode door actuator.

Connector & terminal

(i48) No. 5 — (E ) No. 3:

Is the measured value less than the specified 
value?

1 

Ω

Go to step 7.

Repair harness 
between A/C con-
trol module and 
mode door actua-
tor.

AC-78

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC) (RHD 

MODEL)

7

CHECK HARNESS CONNECTOR BETWEEN 
A/C CONTROL MODULE AND MODE DOOR 
ACTUATOR.
Measure resistance of harness between A/C 
control module and mode door actuator.

Connector & terminal

(i48) No. 10 — (E) No. 1:

Is the measured value less than the specified 
value?

1 

Ω

Go to step 8.

Repair harness 
between A/C con-
trol module and 
mode door actua-
tor.

8

CHECK HARNESS CONNECTOR BETWEEN 
A/C CONTROL MODULE AND MODE DOOR 
ACTUATOR.
Measure resistance of harness between A/C 
control module and mode door actuator.

Connector & terminal

(i48) No. 8 — (E) No. 7:

Is the measured value less than the specified 
value?

1 

Ω

Go to step 9.

Repair harness 
between A/C con-
trol module and 
mode door actua-
tor.

9

CHECK HARNESS CONNECTOR BETWEEN 
A/C CONTROL MODULE AND MODE DOOR 
ACTUATOR.
Measure resistance of harness between A/C 
control module and mode door actuator.

Connector & terminal

(i48) No. 16 — (E) No. 6:

Is the measured value less than the specified 
value?

1 

Ω

Go to step 10.

Repair harness 
between A/C con-
trol module and 
mode door actua-
tor.

10

CHECK POOR CONTACT.
Check poor contact in A/C control module.
Is there poor connection in connector?

There is no poor connection.

Replace A/C con-
trol module.

Repair connector.

Step

Value

Yes

No

AC-79

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

SYMPTOM RELATED DIAGNOSTIC

12.Symptom Related Diagnostic

A: GENERAL DIAGNOSTICS TABLE

AC-00378

Air mix door actuator and potentiometer
(including links) 

Mode door actuator and potentiometer
(including links)

Intake door actuator and
potentiometer (including links)

Fuses (M/B No. 2, F/B No. 17)

Poor connector contacts

Ground

A/C control module

Blower fan motor

Power transistor & fuse

Blower fan relay

A/C relay

Magnet clutch

Radiator fan motors (Main and sub)

Radiator fan relays (Main and sub)

In-vehicle sensor aspirator duct

Sensors (In-vehicle, ambient, water temperature,
evaporator, sunload, etc.)

Component parts

Symptom

Previous mode immediately before

resetting operation is not retained in memory.

A/C system fails to operate when

IG SW is turned "ON".

Burned-out fuse.

No indication appears on display.

Blower motor does not rotate or

rotates erroneously.

Compartment temperature does not decrease

(No cool air is discharged).

Air vents cannot be switched.

Compartment temperature does not quickly

respond to the set value.

Illumination does not dim at night.

A/C does not change from

"Fresh" to "Recirc" or vise versa.

Compartment temperature is higher than

or lower than the set value.

Compartment temperature does not increase

(No hot air is discharged).

Condenser fan does not operate

during A/C operation.