Mitsubishi MSC-A07YV, MSC-A09YV, MSC-A12YV User Manual

SERVICE MANUAL

HFC

utilized

R410A

SPLIT-TYPE, AIR CONDITIONERS
SPLIT-TYPE, HEAT PUMP AIR CONDITIONERS

Wireless type
Models

E1

E1

E1

(WH)

(WH)

(WH)

MSC-A07YV ­MSC-A09YV ­MSC-A12YV -

No. OB329

Indication of model name

MSC-A07YV ­MSC-A09YV ­MSC-A12YV -

NOTE:

•This manual describes technical data of indoor units.

•As for outdoor units MU-A07/A09/A12YV - , refer to the service manual OB330.

•As for outdoor units MUH-A07/A09/A12YV - , refer to the service manual OB331.

•As for outdoor units MUX-A10/A19/A20/A25/A26WV - , refer to the service manual OB307 REVISED
EDITION-A.

•As for outdoor units MUX-A22WV - , refer to the service manual OB318.

•As for outdoor units MXZ-A18/A26/A32WV - , refer to the service manual OB319.

E1
E1
E1

E1

E1

E1

E1

CONTENTS

1. TECHNICAL CHANGES ····································3

2. PART NAMES AND FUNCTIONS······················3

3. SPECIFICATION·················································5

4. NOISE CRITERIA CURVES·······························6

5. OUTLINES AND DIMENSIONS·························7

6. WIRING DIAGRAM ············································8

7. REFRIGERANT SYSTEM DIAGRAM················8

8. MICROPROCESSOR CONTROL ······················9

9. SERVICE FUNCTIONS ····································17

10. TROUBLESHOOTING ······································19

11. DISASSEMBLY INSTRUCTIONS·····················26

12. PARTS LIST······················································28

E1

1

TECHNICAL CHANGES

MSC-A07WV- ➔MSC-A07YV-

MSC-A09WV- ➔MSC-A09YV­MSC-A12WV- ➔MSC-A12YV-

1. Design of front panel has changed.

2. Air filter has changed to the catechin air filter.

2

MSC-A07YV ­MSC-A09YV ­MSC-A12YV -

PART NAMES AND FUNCTIONS

E1

E1

E1

E1E1

E1E1

E1E1

INDOOR UNIT

Air cleaning filter
(white bellows type)

Panel

Catechin air filter
(With deodorizer)

Air outlet

Vertical vanes

Fan

Horizontal vane

Operation section

(When the front panel is opened)

Front panel
Air inlet

to Breaker

Power supply cord

Remote control
receiving section

Remote controller

Display section

Emergency operation switch

Operation indicator lamp
Remote control

receiving section

3

MSC-A07YV-

Installation plate
Installation plate fixing screw 4 o 25 mm
Remote controller holder
Fixing screw for 3 3.5 o 16 mm
Battery (AAA) for remote controller
Wireless remote controller
Felt tape (Used for left or left-rear piping)
Air cleaning filter

1
5
1
2
2
1
1
1

<Indoor unit>

1

2

3

4

5

6

7

8

ON/OFF

FAN

TOO

WARM

TOO

COOL

VANE

MODE

ECONO COOL

STOP

START

HR.

MIN.

I FEEL

COOL

DRY

PM

CLOCK

AM

RESET

CLOCK

HEAT
/FAN

/

Open the front lid.

ON/OFF

TOO

COOL

PM

AM

TOO

WARM

Signal transmitting section

Operation display section

OPERATE /STOP

(ON /OFF)button

TEMPERATURE buttons

Indication of remote controller model is
on back.

OPERATION SELECT button

FAN SPEED CONTROL button

OFF-TIMER button

HR. button

MIN. button

(TIME SET button)

ON-TIMER button

RESET button

ECONO COOL button

VANE CONTROL button

CLOCK SET button

MSC-A09YV­MSC-A12YV-

E1
E1
E1

ACCESSORIES

REMOTE CONTROLLER

4

3

Indoor model

Function

Indoor unit power supply

Air flow(High/Med. /Low )
Power outlet
Running current
Power input
Power factor
Fan motor current
Model
Winding
resistance(at 20:)
Dimensions WOHOD
Weight
Air direction
Sound level(High/Med. /Low )
Fan speed(High/Med. /Low )
Fan speed regulator
Thermistor RT11(at 25:)
Thermistor RT12(at 25:)
Remote controller model

K /h

A

A
W
%

A

"

mm

kg

dB

rpm

k"
k"

MSC-A07YV -

E1

Single phase

230V,50Hz

10

0.17
35
90

0.17

RC4V19-LA
WHT-BLK 413
BLK-RED 334
815O278O244

9
5

3
10
10

KP1A or KG3A

Cooling

474/372 /276

36/31 /25

900/750 /600

Heating

510/420 /342

36/31 /25

950/820 /700

MSC-A09YV -

E1

Single phase

230V,50Hz

10

0.17
35
90

0.17

RC4V19-LA
WHT-BLK 413
BLK-RED 334
815O278O244

9
5

3
10
10

KP1A or KG3A

Cooling

474/384 /306

36/31 /25

900/770 /650

Heating

588/456 /342

39/32 /25

1,050/870 /700

MSC-A12YV -

E1

Single phase

230V,50Hz

10

0.19
40
92

0.19

RC4V19-KA
WHT-BLK 316
BLK-RED 299
815O278O244

10

5

3
10
10

KP1A or KG3A

Cooling

582/444 /324

40/33 /26

930/760 /600

Heating

606/498 /396

39/33 /26

960/830 /700

Electrical

data

Fan

motor

Special

remarks

Capacity

ww

ww

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

SPECIFICATION

NOTE: 1. Test conditions are based on ISO 5151.

Cooling : Indoor DB27°C WB19°C Heating : Indoor DB20°C
Outdoor DB35°C WB24°C OutdoorDB 7°C/WB 6°C
Indoor-Outdoor piping length 5m

2.Remote controller model KP1A and KG3A are the same in terms of specification.
W Reference value

5

4

90

80

70

60

50

40

30

20

10

63 125 250 500 1000 2000 4000 8000

APPROXIMATE
TERESHOLD OF
HEARING FOR
CONTINUOUS
NOISE

NC-60

NC-50

NC-40

NC-30

NC-20

NC-70

OCTAVE BAND SOUND PRESSURE LEVEL, dB re 0.0002 MICRO BAR

BAND CENTER FREQUENCIES, Hz

Test conditions,

Cooling : DB27: WB19:
Heating : DB20: WB -:

MSC-A07YV- E1

COOL

High

FUNCTIONFAN SPEED

36

HEAT

SPL(dB

(A)) LINE

90

80

70

60

50

40

30

20

10

63 125 250 500 1000 2000 4000 8000

APPROXIMATE
TERESHOLD OF
HEARING FOR
CONTINUOUS
NOISE

NC-60

NC-50

NC-40

NC-30

NC-20

NC-70

OCTAVE BAND SOUND PRESSURE LEVEL, dB re 0.0002 MICRO BAR

BAND CENTER FREQUENCIES, Hz

Test conditions.

Cooling : DB27: WB19:
Heating : DB20: WB -:

MSC-A09YV- E1

COOL

High

FUNCTIONFAN SPEED

36

HEAT 39

SPL(dB

(A)) LINE

90

80

70

60

50

40

30

20

10

63 125 250 500 1000 2000 4000 8000

APPROXIMATE
TERESHOLD OF
HEARING FOR
CONTINUOUS
NOISE

NC-60

NC-50

NC-40

NC-30

NC-20

NC-70

OCTAVE BAND SOUND PRESSURE LEVEL, dB re 0.0002 MICRO BAR

BAND CENTER FREQUENCIES, Hz

Test conditions,

Cooling : DB27: WB19:

MSC-A12YV- E1

COOL

FUNCTIONFAN SPEED

40

HEAT

High

39

SPL(dB

(A)) LINE

INDOORUNIT

WALL

MICROPHONE

0.8m

1m

NOISE CRITERIA CURVES

6

5

OUTLINES AND DIMENSIONS

MSC-A07YV ­MSC-A09YV -

INDOOR UNIT

278

60

58

162

E1

E1

Installation plate

Indoor unit

783

815

606

149

19

Power supply cord
Lead to right 1.0m
Lead to left 0.3m

81.5

41

81.5

Air in

30

Air out

326326

242 5

7 or more

90

110

244

133.5

231.5

42

2.5

81.5

Wall hole

Installation plate

Liquid line
Gas line

{

Insulation

Drain hose
(Connected part O,D)

Insulation

[65

[6.35-0.5m

[9.52-0.43m

[37 O.D

[21 I.D

[16

[28

4.5

271

Unit: mm

Wireless remote controller

MSC-A12YV -

INDOOR UNIT

278

60

58

162

E1

Installation plate

783

815

606

19

Indoor unit

41

Air in

149

Power supply cord
Lead to right 1.0m
Lead to left 0.3m

30

Air out

242

7 or more

244

326326

5

Installation plate

Liquid line
Gas line

{

Insulation

90

110

161.5161.5

17.5

258

218.5

42

2.5

81.581.5
Wall hole

[9.52-0.43m

Drain hose
(Connected part O,D)

Insulation

[65

[6.35-0.5m

[37 O.D

[21 I.D

[16

[28

Wireless remote controller

7

6

SYMBOL

NR11
RT11
RT12

SR141

NAME

NAME NAME
INDOOR FAN CAPACITOR
FUSE(3.15A)
INDOOR FAN MOTOR (INNER FUSE)
VANE MOTOR

VARISTOR
ROOM TEMPERATURE THERMIST OR
INDOOR COIL THERMISTOR
SOLID STATE RELAY

TERMINAL BLOCK

SYMBOL

C11
F11

MF

MV

SYMBOL

TB

T11

TRANSFORMER

CIRCUIT BREAKER

SR141

C11

RED

WHT

3

6

5

BRN

YLW

GRY

BLK

4

3

2

1

MF

121

CN

1
3
5

111

CN

112

CN

RT12

RT11

NR11

F11

ELECTRONIC CONTROL P.C. BOARD

CN211

TAB12
CN201

3
2
1

CN202

2
1

151

CN

5

5

BRN
RED

BLU

WHT
BLK

BLU

BRN

TB

L
3
N
2
1

12V

TO OUTDOOR
UNIT
CONNECTING

POWER
SUPPLY
CORD
~/N 230V
50Hz

GRN/YLW

POWER MONITOR,
RECEIVER
P.C.BOARD

REMOTE
CONTROLLER

MV

FOR
MUH OR
MXZ TYPE

FOR
MU OR
MUX TYPE

12V

PE

101

CN

T11

GRN

LD103

WIRING DIAGRAM

MSC-A07YV - MSC-A09YV - MSC-A12YV -

INDOOR UNIT

MODELS WIRING DIAGRAM

E1E1E1

NOTE:1. About the outdoor side electric wiring refer to the outdoor unit electric wiring diagram for servicing.

2. Use copper conductors only. (For field wiring)

3. Symbols below indicate.

/: Terminal block, : Connector

7

MSC-A07YV - MSC-A09YV -

INDOOR UNIT

Indoor
heat
exchanger

REFRIGERANT SYSTEM DIAGRAM

E1E1

Refrigerant pipe [9.52
(with heat insulator)

Indoor coil
thermistor
RT12

Flared connection

MSC-A12YV -

INDOOR UNIT

Indoor
heat
exchanger

Room temperature

Room temperature
thermistor
RT11

Refrigerant flow
in cooling

Flared connection

Refrigerant pipe [6.35
(with heat insulator)

thermistor
RT11

8

E1

Indoor coil
thermistor

Refrigerant flow
in cooling

Refrigerant pipe [12.7
(with heat insulator)

RT12

Flared connection

Flared connection

Refrigerant pipe [6.35
(with heat insulator)

Unit:mm

8

ON/OFF

FAN

TOO

WARM

TOO

COOL

VANE

MODE

ECONO COOL

STOP

START

HR.

MIN.

I FEEL

COOL

DRY

PM

CLOCK

AM

RESET

CLOCK

HEAT
/FAN

/

Open the front lid.

ON/OFF

TOO
COOL

PM

AM

TOO

WARM

Signal transmitting section

Operation display section

OPERATE /STOP
(ON /OFF)button

TEMPERATURE buttons

OPERATION SELECT button

FAN SPEED CONTROL button

OFF-TIMER button

HR. button

MIN. button

(TIME SET button)

ON-TIMER button

RESET button

ECONO COOL button

VANE CONTROL button

CLOCK SET button

MICROPROCESSOR CONTROL

MSC-A07YV ­MSC-A09YV ­MSC-A12YV -

E1

E1

E1

Once the operation mode are set, the same operation mode can be repeated by simply turning the OPERATE/STOP
(ON/OFF) button ON. Indoor unit receives the signal with a beep tone.
When the system turns off, 3-minute time delay will operate to protect system from overload and compressor will not restart for
3 minutes.

WIRELESS REMOTE CONTROLLER

INDOOR UNIT DISPLAY SECTION

Operation Indicator lamp

The operation indicator at the right side of the indoor
unit indicates the operation state.

• The following indication does not
depend on the shape of lamp.

Operation Indicator

lighted
not lighted

Difference
between target

Operation stateIndication

This shows that the
air conditioner is
operating to reach
the target temperature.
Please wait until the
target temperature is
obtained.

temperature
and room
temperature

Approx. 2 : 
or more

8-1. COOL ( ) OPERATION

(1) Press OPERATE/STOP(ON/OFF) button. OPERATION INDICATOR lamp of the indoor unit turns on with a beep tone.
(2) Select COOL mode with the OPERATION SELECT button.
(3) Press TEMPERATURE buttons (TOO WARM or TOO COOL button)to select the desired temperature.

The setting range is 16 ~ 31°C

1. Thermostat control

Thermostat is ON or OFF by difference between room temperature and set temperature

Room temperature minus set temperature : 0.3 : or more················································ON
Room temperature minus set temperature : less than -0.3 :············································OFF

2. Indoor fan speed control

Indoor fan operates continuously at the set speed by FAN SPEED CONTROL button regardless
of thermostat’s OFF-ON.

In Auto the fan speed is as follows.

Room temperature minus set temperature : 1.7 degrees or more·······························High
Room temperature minus set temperature : Between 1 and 1.7 degrees···················Med.
Room temperature minus set temperature : less than 1 degree··································Low

This shows that the
room temperature is
approaching the

Approx. 2 : 
or less

target temperature.

Initial temperature difference Thermostat

Difference between room
temperature and set tem­perature during operation

Set temperature

-0.3 :

0.3 :

Difference between room

Initial temperature difference

9

Fan speed

temperature and set tem­perature during operation

3 deg.

1.7 deg.

1 deg.

35

30

25

20

15

10

:

10 15 20 25 30 35

Set temperature

Initial room temperature

Set temperature and
initial room temperature in dry mode

:

3. Coil frost prevention

① Temperature control

When the indoor coil thermistor RT12 reads 4°C or below(MSC-A07/A09YV) / 0°C or below(MSC-A12YV) for 5 minutes, the
coil frost prevention mode starts.

The indoor fan operates at the set speed and the compressor stops for 5 minutes.
After that, if RT12 still reads below 4°C (MSC-A07/A09YV) / 0°C (MSC-A12YV), this mode is prolonged until the RT12
reads over 4°C (MSC-A07/A09YV) / 0°C (MSC-A12YV).

② Time control

When the three conditions as follows have been satisfied for 1 hour and 45 minutes, the compressor stops for 3 minutes.
The indoor fan operates at the set speed.
a. Compressor has been continuously operating.
b. Indoor fan speed is Low or Med.
c. Room temperature is below 26°C.
When compressor stops, the accumulated time is cancelled. When compressor restarts, time counting starts
from the beginning.
Time counting also stops temporarily when the indoor fan speed becomes High or the room temperature exceeds
26°C. However, when two of the above conditions (b.and c.) are satisfied again, time accumulation is resumed.

Operation chart

Example

ON

ON

Compressor

OFF

Outdoor fan

ON

Indoor fan

( continuously at set speed)

8-2. DRY ( ) OPERATION

(1) Press OPERATE/STOP(ON/OFF) button.

OPERATION INDICATOR lamp of the indoor unit turns on with a beep tone.
(2) Select DRY mode with the OPERATION SELECT button.
(3) The microprocessor reads the room temperature and determines the set tem-

perature. Set temperature is as shown on the right chart.

DRY operation will not function when the room temperature is 13°C or below.
(4) When DRY operation functions the fan speed is lower than COOL operation

except at (fan speed) Low.

The system for dry operation uses the same refrigerant circuit as the cooling
circuit.
The compressor and the indoor fan are controlled by the room temperature.

1. Thermostat control

Thermostat is ON or OFF by difference between room temperature and set temperature.

Initial temperature difference Thermostat
Room temperature minus set temperature : 0.3 : or more················································ON
Room temperature minus set temperature : less than -0.3 :············································OFF

2. Indoor fan speed control

Indoor fan operates at the set speed by FAN SPEED CONTROL button.
In Auto fan speed becomes Low.

3. The operation of the compressor and indoor / outdoor fan
<MU-A07/A09/A12YV, MUH-A07/A09/A12YV, MUX-A10/A19/A20/A22/A25/A26WV>

Compressor operates by room temperature control and time control.
Indoor fan and outdoor fan operate in the same cycle as the compressor.

● When the room temperature is 23°C or over:

When the thermostat is ON, the compressor repeats 8 minutes ON and 3 minutes OFF.
When the thermostat is OFF, the compressor repeats 4 minutes OFF and 1 minute ON.

● When the room temperature is under 23°C.

When the thermostat is ON, the compressor repeats 2 minutes ON and 3 minutes OFF.
When the thermostat is OFF, the compressor repeats 4 minutes OFF and 1 minute ON.

OFF

10

Difference between room
temperature and set tem­perature during operation

Set temperature

-0.3 :

0.3 :

Operation time chart

Released

Cold Air Prevention

18: 22:

Fan speed

Set speed
Very Low or stop

Example

Thermostat

OFF

ON

ON

OFF

OFF

ON

ON

3 min.

ON

OFF

ON

OFF

4 min.

Indoor fan

Outdoor fan
Compressor

ON

OFFOFF

ON

OFF

8 min. 1 min.

4. Coil frost prevention

The operation is as same as coil frost prevention during COOL operation.(Refer to 8-1.3.)
However when coil frost prevention works while the indoor fan is OFF, its speed becomes set speed.

8-3. FAN ( ) OPERATION <MU-A07/A09/A12YV, MUX-A10/A19/A20/A22/A25/A26WV>

(1) Press OPERATE/STOP(ON/OFF) button. OPERATION INDICATOR lamp of the indoor unit turns on with a beep tone.
(2) Select FAN mode with the OPERATION SELECT button.
(3) Select the desired fan speed. When AUTO, it becomes Low.

Only indoor fan operates.
Outdoor unit does not operate.

8-4. HEAT ( ) OPERATION <MUH-A07/A09/A12YV, MXZ-A18/A26/A32WV>

(1) Press OPERATE/STOP(ON/OFF) button.

OPERATION INDICATOR lamp of the indoor unit turns on with a beep tone.
(2) Select HEAT mode with the OPERATION SELECT button.
(3) Press TEMPERATURE buttons (TOO WARM or TOO COOL button) to select the desired temperature.

The setting range is 16 ~ 31°C.

1. Thermostat control

Thermostat is ON or OFF by difference between room temperature and set temperature.

Initial temperature difference Thermostat
Room temperature minus set temperature : less than -0.3 :··············································ON
Room temperature minus set temperature : 0.3 : or more·················································OFF

Difference between room
temperature and set tem­perature during operation

Set temperature

-0.3 deg.

0.3 deg.

2. Indoor fan speed control

(1) Indoor fan operates at the set speed by FAN SPEED CONTROL button.

In Auto the fan speed is as follows.

Initial temperature difference

Fan speed

Difference between room
temperature and set tem­perature during operation

Set temperature minus room temperature: 1.7 degrees or more·············································· High
Set temperature minus room temperature: Between 1 and 1.7 degrees·································· Med.
Set temperature minus room temperature: less than 1 degree················································· Low

1 deg.

1.7 deg.

(2) Cold air prevention control

1 When the compressor is not operating,

(1) if the temperature of indoor coil thermistor RT12 is 0°C or less, the fan stops.
(2) if the temperature of indoor coil thermistor RT12 is more than 0°C, the fan operates at Very Low.

2 When the compressor is operating,

(1) if the temperature of RT12 is 22°C or more, the fan operates at set speed.
(2) if the temperature of RT12 is less than 22°C and

(1) if the temperature of room temperature thermistor RT11 is 15°C or less, the fan stops.
(2) if the temperature of room temperature thermistor RT11 is more than 15°C, the fan operates at Very Low.

NOTE : If the temperature of RT12 reads from 18°C to 22°C at the air conditioner stating and also after defrosting,

this control works.

11

3 deg.

(3) Warm air control.

<Time condition>

<Indoor fan speed>

less than 2 minutes Low
2 minutes to 4 minutes Med.
more than 4 minutes High

Mode

COOL mode of

"I FEEL CONTROL"

DRY mode of

"I FEEL CONTROL"

HEAT mode of

"I FEEL CONTROL"

Initial room temperature

MUH &MXZ type

25: or more

23:or more,

less than 25:
less than 23:

MU & MUX type

25: or more

more than13:,

less than 25:

When the following any condition of 1 (a. ~ c.) and the condition of 2 are satisfied at the same time, warm air control
works.

1 a.) When outdoor unit starts operating in HEAT mode.

b.) When cold air prevention has been released.

c.) When defrosting has been finished

2 When the temperature of indoor coil thermistor RT12 is less than 37°C.
When warm air control works, the fan speed changes as follows to blow out warm air gradually.

Gradation of fan speed in initial

The upper limit of the fan speed in MANUAL is the set speed.
The upper limit of the fan speed in AUTO is the speed decided by indoor fan speed control.(Refer to 8-4.2.(1).)
When the temperature of RT12 has been 37°C or more, or when the set speed has been changed, this control is
released and the fan speed is the set speed.

NOTE: As for high pressure protection, defrosting and R.V. coil control, refer to service manual for outdoor unit.

8-5. “I FEEL CONTROL” ( ) OPERATION

(1) Press OPERATE/STOP(ON/OFF) button.

OPERATION INDICATOR lamp of the indoor unit turns on
with a beep tone.

(2) Select “I FEEL CONTROL”( ) mode with the OPERA-

TION SELECT button.

(3) The operation mode is determined by the initial room tem-

perature at start-up of the operation, as shown on the
right table.

● Once the mode is fixed, the mode does not change by room temperature afterwards.

● Under the ON-TIMER ( ) operation, mode is determined according to the room temperature at set time the opera-

tion starts.

● When the system is stopped on the remote controller and restarted within 2 hours in “I FEEL CONTROL” ( ) mode,
the system operates in previous mode automatically regardless of the room temperature.

Operation time chart

Example

Previous operation

COOL mode of
“I FEEL CONTROL”
or COOL mode

When the system is restarted after 2 hours and more, the operation mode is determined by the room temperature at

start-up of the operation.

Operation time chart

Example

Previous operation

COOL mode of
“I FEEL CONTROL”

or COOL mode

Restart

COOL mode of
“I FEEL CONTROL”

Restart

COOL or DRY or
HEAT mode of “I FEEL
CONTROL” that deter­mined by room tem­perature at start-up of
the operation.

12

(4) The initial set temperature is decided by the initial room temperature.

TOO

COOL

TOO

WARM

Mode

COOL mode of

"I FEEL CONTROL"

DRY mode of

"I FEEL CONTROL"

HEAT mode of

"I FEEL CONTROL"

MU & MUX type

more than 13:,

Initial room temperature

26: or more

25: or more,
less than 26:

less than 25:

MUH & MXZ type

26: or more

25: or more,

less than 26:

23: or more,
less than25:

less than 23:

Initial set temperature

24:

❈1

Initial room temperature
minus 2:

Initial room temperature
minus 2:

26:

❈1 When the system is restarted with the remote controller, the system operates with the previous set temperature regard-

less of the room temperature at restart.

(5) TEMPERATURES buttons

In “I FEEL CONTROL” ( ) mode, set temperature is decided by the microprocessor based on the room temperature.
In addition, set temperature can be controlled by TOO WARM or TOO COOL buttons when you feel too cool or too
warm. Each time the TOO WARM or TOO COOL button is pressed, the indoor unit receives the signal and emits a beep
tone.

● Fuzzy control

When the TOO COOL or TOO WARM button is pressed, the microprocessor changes the set temperature, considering
the room temperature, the frequency of pressing TOO COOL or TOO WARM button and the user’s preference to heat or
cool. So this is called “Fuzzy control”, and works only in “I FEEL CONTROL” mode.
In DRY mode of “I FEEL CONTROL”, the set temperature doesn’t change.

…

To raise the set temperature 1~2 degrees(°C)

…

To lower the set temperature 1~2 degrees(°C)

8-5-1. COOL mode of “I FEEL CONTROL”

1. Thermostat control

Thermostat control is as same as COOL OPERATION.(8-1.1.)

2. Indoor fan speed control

Indoor fan speed control is as same as COOL OPERATION.(8-1.2.)

3. Coil frost prevention

Coil frost prevention is as same as COOL OPERATION.(8-1.3.)

8-5-2. DRY mode of “I FEEL CONTROL”

1. Thermostat control

Thermostat control is as same as DRY OPERATION.(8-2.1.)

2. Indoor fan speed control

Indoor fan speed control is as same as DRY OPERATION.(8-2.2.)

3. The operation of the compressor and indoor/outdoor fan

The operation of the compressor and indoor/outdoor fan is as same as DRY OPERATION.(8-2.3.)

4. Coil frost prevention

Coil frost prevention is as same as DRY OPERATION.(8-2.4.)

8-5-3. HEAT mode of “I FEEL CONTROL” <MUH-A07/A09/A12YV, MXZ-A18/A26/A32WV>

1. Thermostat control

Thermostat control is as same as HEAT OPERATION.(8-4.1.)

2. Indoor fan speed control

Indoor fan speed control is as same as HEAT OPERATION.(8-4.2.)

NOTE: As for high pressure protection, defrosting and R.V. coil control, refer to service manual for outdoor unit.

13

High High

Med.

Low

8-6. FAN MOTOR CONTROL

(1) Rotational frequency feedback control

The indoor fan motor is equipped with a rotational frequency sensor, and outputs signal to the microprocessor to
feedback the rotational frequency. Comparing the current rotational frequency with the target rotational
frequency (High,Med.,Low), the microprocessor controls SR141 and adjusts fan motor electric current to make the
current rotational frequency close to the target rotational frequency. With this control, when the fan speed is switched,
the rotational frequency changes smoothly.

(2) Fan motor lock-up protection

When the rotational frequency feedback signal is not output for 12 seconds, (or when the microprocessor cannot detect
the signal for 12 seconds) the fan motor is regarded locked-up. Then the electric current to the fan motor is shut off. 3 min­utes later, the electric current is applied to the fan motor again. During the fan motor lock-up, the OPERATION INDICA­TOR lamp flashes on and off to show the fan motor abnormality. (Refer to page 21.)

8-7. AUTO VANE OPERATION

(1) Vane motor drive

These models are equipped with a stepping motor for the horizontal vane. The rotating direction, speed, and angle of
the motor are controlled by pulse signals (approx. 12V) transmitted from indoor microprocessor.

(2) The horizontal vane angle and mode changes as follows by pressing the VANE CONTROL button.

(3) Positioning

The vane is once pressed to the vane stopper below to confirm the standard position and then set to the desired angle.
Confirming of standard position is performed in case of follows.
(a) When the OPERATE/STOP(ON/OFF) button is pressed.
(b) When the vane control is changed from AUTO to MANUAL.
(c) When the SWING is finished.
(d) When the test run starts.
(e) When the power supply turns ON.

(4) VANE AUTO ( ) mode

In VANE AUTO mode, the microprocessor automatically determines the vane angle to make the optimum room-temper­ature distribution.

1 In COOL and DRY operation

Vane angle is fixed to Angle 1.

2 In FAN operation

<MU-A07/A09/A12YV,

MUX-A10/A19/A20/A22/A25/A26WV

2 In HEAT operation

<MUH-A07/A09/A12YV, MXZ-A18/A26/A32WV>

(5) Dew prevention

During COOL or DRY operation at Vane Angle 4 or 5 when the cumulative operation time of compressor exceeds 1
hour, the vane angle automatically changes to Angle 1 for dew prevention.

(6) SWING MODE ( )

By selecting SWING mode with the VANE CONTROLbutton, the horizontal vane swings vertically. The remote controller
displays “ ”.

>

Vane angle is fixed to Angle 4.

14

(7) Cold air prevention in HEAT operation <MUH-A07/A09/A12YV, MXZ-A18/A26/A32WV>

Set position

Angle 1

Released

Cold air prevention

24:

28:

When any of the following conditions occurs in HEAT operation, the horizontal vane angle changes to Angle 1 automat­ically to prevent cold air blowing on users.

① Compressor is not operating.
➁ Defrosting is performed.
➂ Indoor coil thermistor RT12 reads 24: or below.
➃ Indoor coil thermistor RT12 temperature is raising from 24°C or below, but it does not exceed 28:.

Indoor coil thermistor
RT12 temperature

NOTE : If the temperature of RT12 reads from 24°C to 28°C at the air conditioner stating , this control works.

(8) ECONO COOL ( ) operation (ECONOmical operation)

When the ECONO COOL button is pressed in COOL mode, set temperature is automatically set 2°C higher than that in
COOL mode.
Also the horizontal vane swings in various cycle according to the temperature of indoor heat exchanger(RT12).
SWING operation makes you feel cooler than set temperature. So, even though the set temperature is higher than that
in COOL mode, the air conditioner can keep comfort. As a result, energy can be saved.
ECONO COOL operation is cancelled when the ECONO COOL button is pressed once again or VANE CONTROLbut­ton is pressed or operation mode is changed.

NOTE : ECONO COOL operation does not work in COOL mode of “I FEEL CONTROL”.

SWING operation

In swing operation of ECONO COOL operation mode, the initial air flow direction is adjusted to “Horizontal”.
According to the temperature of indoor coil thermistor RT12 at starting of this operation, next downward blow time is
decided. Then when the downward blow has been finished, next upward blow time is decided.
For initial 10 min. the swing operation is performed in table G~H for quick cooling.
Also, after 10 min. when the difference of set temperature and room temperature is more than 2 degrees, the swing
operation is performed in table D~H for more cooling.
The air conditioner repeats the swing operation in various cycle as follows.

Horizontal vane

Temperature of indoor

coil thermistor RT12

A
B

C

D
E
F

G
H

15°C or less
15°C to 17°C
17°C to 18°C

18°C to 20°C

20°C to 21°C
21°C to 22°C
22°C to 24°C

more than 24°C

Downward blow time

(sec.)

2
5
8

11
14
17

20
23

Horizontal blow time

(sec.)

23
20
17
14
11

8
5
2

8-8. TIMER OPERATION

1. How to set the timer

(1) Press OPERATE/STOP(ON/OFF) button to start the air conditioner.
(2) Check that the current time is set correctly.
NOTE : Timer operation will not work without setting the current time. Initially “AM0:00” blinks at the current time display

of TIME MONITOR, so set the current time correctly with CLOCK SET button.

(3) Press ON or OFF TIMER buttons to select the operation.

“ ” button... AUTO START operation (ON timer)
“ ” button... AUTO STOP operation (OFF timer)

15

EMERGENCY OPERATION switch

PM

AM

PM

PM

(4) Press HR. and MIN. button to set the timer. Time setting is 10-minute units.

HR. and MIN. button will work when “ ” or “ ” mark is flashing.
These marks disappear in 1 minute.
After setting the ON timer, check that OPERATION INDICATOR lamp of the indoor unit lights.

NOTE1 : Be sure to place the remote controller at the position where its signal can reach the air conditioner even during

TIMER operation, or the set time may deviate within the range of about 10 minutes.

NOTE2 : Reset the timer in the following cases, or the set time may deviate and other malfunctions may occur.

● A power failure occurs.

● The circuit breaker functions.

2. Cancel

TIMER setting can be cancelled with the ON or OFF TIMER buttons. (“ ” or “ ”)
To cancel the ON timer, press the “ ” button.

To cancel the OFF timer, press the “ ” button.
TIMER is cancelled and the display of set time disappears.

PROGRAM TIMER

● The OFF timer and ON timer can be used in combination.

● “ ” and “ ” display shows the order of the OFF timer and ON timer operation.

(Example 1) The current time is 8:00 PM.

The unit turns off at 11:00 PM, and on at 6:00 AM.

(Example 2) The current time is 11:00 AM.

The unit turns on at 5:00 PM, and off at 9:00 PM.

NOTE : TIMER setting will be cancelled by power failure or breaker functioning.

8-9. EMERGENCY-TEST OPERATION

In case of test run operation or emergency operation, use the EMERGENCY OPERATION switch on the front of the
indoor unit. Emergency operation is available when the remote controller is missing, has failed or the batteries of remote
controller run down. The unit will start and the OPERATION INDICATOR lamp will light.
The first 30 minutes of operation is the test run operation. This operation is for servicing. The indoor fan speed runs at
High speed and the system is in continuous operation. (The thermostat is ON.)
After 30 minutes of test run operation the system shifts to EMERGENCY COOL [/ HEAT<MUH-A07/A09/A12YV, MXZ­A18/A26/A32WV>] MODE with a set temperature of 24°C. The fan speed shifts to Med. speed.
The coil frost prevention works even in emergency operation [, and defrosting<MUH-A07/A09/A12YV, MXZ­A18/A26/A32WV> too].

In the test run or emergency operation, the horizontal vane operates in VANE AUTO ( ) mode.
Emergency operation continues until the EMERGENCY OPERATION switch is pressed once again
(MU-A07/A09/A12YV, MUX-A10/A19/A20/A22/A25/A26WV)/once or twice (MUH-A07/A09/A12YV, MXZ-A18/A26/A32WV)
or the unit receives any signal from the remote controller.

In case of latter normal operation will start.

NOTE : Do not press the EMERGENCY OPERATION switch during normal operation.

• The following indication does not depend on the
shape of lamp.

Press once <Cool>

OPERATION INDICATOR lamp

Press again <Heat>
Press once again <Stop>

w Heat is available only in MUH-A07/A09/A12YV and

MXZ-A18/A26/A32WV.

16

9

No. 1 unit
No. 2 unit
No. 3 unit
No. 4 unit

1 unit operation
No modification

–
–
–

2 units operation

Same as at left

Solder J1

–
–

3 units operation

Same as at left
Same as at left

Solder J2

–

4 units operation

Same as at left
Same as at left
Same as at left

Solder both J1 and J2

SERVICE FUNCTIONS

MSC-A07YV ­MSC-A09YV ­MSC-A12YV -

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9-1. TIMER SHORT MODE

For service, set time can be shortened by short circuit of JPG and JPS the electronic control P.C. board.
The time will be shortened as follows. (Refer to page 25.)

Set time : 1 minute ➔ 1-second
Set time : 3 minutes ➔ 3-second (It takes 3 minutes for the compressor to start operation. However, the starting time is

shortened by short circuit of JPG and JPS.)

9-2. P.C. BOARD MODIFICATION FOR INDIVIDUAL OPERATION

A maximum of 4 indoor units with wireless remote controllers can be used in a room.
In this case, to operate each indoor unit individually by each remote controller, P.C. boards of remote controller must be
modified according to the number of the indoor unit.

How to modify the remote controller P.C. board

Remove batteries before modification. The board has a print as shown below :

Remote controller model : KP1A

J2

J1

Remote controller model : KG3A

The P.C. board has the print “J1” and “J2”. Solder “J1” and “J2” according to the number of indoor unit as shown in Table 1.
After modification, press the RESET button.

J2

NOTE : 1. For remodelling, take out the

batteries and press the
OPERATE/STOP(ON/OFF)
button twice or 3 times at first.

J1

After finish remodelling, put
back the batteries then press
the RESET button.

2. Remote controller model KP1A
and KG3A are the same in
terms of specification.

Table 1

How to set the remote controller exclusively for particular indoor unit

After you turn the breaker ON, the first remote controller that sends the signal to the indoor unit will be regarded as the
remote controller for the indoor unit.
The indoor unit will only accepts the signal from the remote controller that has been assigned to the indoor unit once they
are set.
The setting will be cancelled if the breaker has turned off, or the power supply has shut down.
Please conduct the above setting once again after the power has restored.

17

SW2-1 sets the AUTO RESTART FUNCTION ON / OFF.
SW2-2 switches over the MU & MUX type / MUH & MXZ type.

When the units are shipped from the factory, SW2 is as follows.
SW2-1: AUTO RESTART FUNCTION ON
SW2-2: MUH & MXZ type

}

12

12

SW2

FRONT

IC101

SW2

CN151

SW1

CN112

CN121

L101

CN201

F11

TAB12

CN202

C11

CN211

1 2

1 2

1 2

SW2 SW2

1 2

Outdoor unit

MUH & MXZ type

Set 2 switch downside.

Outdoor unit

MU & MUX type

Set 2 switch upside.

1 2

SW2 SW2

1 2

1 2

1 2

AUTO RESTART

FUNCTION ON

Set 1 switch downside.

AUTO RESTART

FUNCTION OFF

Set 1 switch upside.

Slide switch

Type

The position
of the slide
switch

COOL ONLYCOOL & HEAT

9-3. REMOTE CONTROLLER (How to set the type)

This remote controller setting needs to be switched according to the type of air conditioner (COOL & HEAT or COOL
ONLY).
If the setting is incorrect, the air conditioner does not operate normally. Therefore, check if the setting corresponds to the
type of air conditioner. If not, correct the setting as shown below.

9-4. MU & MUX TYPE / MUH & MXZ TYPE SWITCH OVER AND AUTO RESTART FUNCTION

1. MU & MUX TYPE / MUH & MXZ TYPE SWITCH OVER

The indoor units for MU & MUX type and MUH & MXZ type
are common specifications. Set switch according to the
type of outdoor unit. The units are set for
MUH & MXZ type when they are shipped from the factory.

How to switch over MU & MUX TYPE / MUH & MXZ TYPE

! Turn off the main power for the unit.
@ Pull out the electronic control P.C. board, and change

switch(SW2-2) on the indoor electronic control P.C. board
according to the type of outdoor unit as following figures.

NOTE:•If the indoor-outdoor connecting wire is incorrectly

connected on the terminal block, the unit does not
operate normally.

2. AUTO RESTART FUNCTION

•If a ground is incorrect, it may cause an electric shock.

When the indoor unit is controlled with the remote controller, the operation mode, set temperature, and the fan speed
are memorized by the indoor electronic control P.C.board. The “AUTO RESTART FUNCTION” sets to work the moment
power has restored after power failure.Then, the unit will restart automatically. However if the unit is operated in “I
FEEL CONTROL” mode before power failure, the operation is not memorized. In “I FEEL CONTROL” mode, the opera­tion is decided by the initial room temperature. “AUTO RESTART FUNCTION” is ON when the units are shipped from
the factory.

How to release “AUTO RESTART FUNCTION”

! Turn off the main power for the unit.
@ Pull out the electronic control P.C. board, and change switch(SW2-1) on the indoor electronic control P.C. board as

following figures.

Operation

! If the main power (230V AC) has been cut, the operation settings remain.
@ After the power is restored, the unit restarts automatically according to the memory. (However, it takes at least 3

minutes for the compressor to start running.)

NOTE

•The operation settings are memorized when 10 seconds have passed after the remote controller was operated.

•If main power is cut while AUTO START/STOP timer is active, the timer setting is cancelled.

•If the unit has been off with the remote controller before power failure, the auto restart function does not work as the

power button of the remote controller is off.

•To prevent breaker off due to the rush of starting current, systematize other home appliance not to turn on at the same

time.

•When some air conditioners are connected to the same supply system, if they are operated before power failure, the

starting current of all the compressors may flow simultaneously at restart.
Therefore, the special counter-measures are required to prevent the main voltage-drop or the rush of the starting current
by adding system that allows the units to start one by one.

18

10

Lead wiring

Housing point

Insert the negative pole
of the batteries first.
Check if the polarity of
the batteries are correct.

HEAT

/FAN

/

RESET button

HEAT

/FAN

/

TROUBLESHOOTING

MSC-A07YV ­MSC-A09YV ­MSC-A12YV -

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10-1. Cautions on troubleshooting

1. Before troubleshooting, check the following:

1) Check the power supply voltage.

2) Check the indoor/outdoor connecting wire for mis-wiring.

2. Take care the following during servicing.

1) Before servicing the air conditioner, be sure to first turn off the remote controller to stop the unit, and then after con­firming the horizontal vane is closed, turn off the breaker and/or disconnect the power plug.

2) Be sure to turn OFF the power supply before removing the front panel, the cabinet, the top panel, and the electronic
control P.C. board.

3) When removing the electronic control P.C. board, hold the edge of the board with care NOT to apply stress on the
components.

4) When connecting or disconnecting the connectors, hold the housing of the connector. DO NOT pull the lead wires.

3. Troubleshooting procedure

1) First, check if the OPERATION INDICATOR lamp on the indoor unit is flashing on and off to indicate an abnormality.
To make sure, check how many times the abnormality indication is flashing on and off before starting service work.

2) If the electronic control P.C. board is supposed to be defective, check the copper foil pattern for disconnection and the
components for bursting and discoloration.

3) When troubleshooting, refer to the flow chart on page 20 and the check table on page 21.

4. How to replace batteries

Weak batteries may cause the remote controller malfunction.

In this case, replace the batteries to operate the remote controller normally.

1 Remove the front lid and insert batteries.

2 Press the RESET button.

Then reattach the front lid.

NOTE1 : If the RESET button is not pressed, the remote controller may not operate correctly.
NOTE2 : INFORMATION FOR MULTI SYSTEM AIR CONDITIONER

(OUTDOOR UNIT : MXZ-A18WV- MXZ-A26WV- MXZ-A32WV- )

E1E1E1

Multi system air conditioner (Outdoor unit MXZ-A18WV- MXZ-A26WV- MXZ-A32WV- ) can connect two or
more indoor units with one outdoor unit.

According to the capacity, two or more units can operate simultaneously.

•When you try to operate two or more indoor units with one outdoor unit simultaneously, one for the cooling and the
other for heating, the operation mode of the indoor unit that operates earlier is selected. The other indoor units that
will start the operation later cannot operate, indicating as shown in the figure below. In this case, please set all the
indoor units to the same operation mode.

Operation Indicator

E1E1E1

lighted

flashing

•When indoor units starts the operation while the defrosting of outdoor unit is being done, it takes a few minutes
(max. 10 minutes) to blow out the warm air.

•In the heating operation, though indoor unit that does not operate may get warm or the sound of refrigerant flowing
may be heard, they are not malfunction. The reason is that the refrigerant continuously flows into it.

19

10-2. Instruction of troubleshooting

Start

Indoor unit
operates.
Outdoor unit
doesn't
operate.

Indoor unit
doesn't receive
the signal from
remote controller.

Indoor unit
operates.
Outdoor unit
doesn't operate
normally.

OPERATION
INDICATOR
lamp on the
indoor unit is
flashing on
and off.

Outdoor unit
operates in
only Test Run
operation.

Outdoor unit
doesn't
operate
even in
Test Run
operation.

Indoor unit
operates,
when the
EMERGENCY
OPERATION
switch is
pressed.

Indoor unit
doesn't operate,
when the
EMERGENCY
OPERATION
switch is
pressed.

Check room
temperature
thermistor.
Refer to
"Test point
diagram and
voltage" on
page 25.

MUH-A07/A09/A12YV
MUX-A19/A20/A22/
A25/A26WV

Refer to
"Check of
outdoor unit".

Refer to B
"Check of
remote
controller
and receiver
P.C. board"
on page 23.

MUH-A07/A09/A12YV
MXZ-A18/A26/A32WV

Flash on and
off at 0.5­second
intervals
Cause:
Indoor/
Outdoor unit

• Mis-wiring

2-time flash
Cause:
Indoor unit

• Trouble of
room temp­ erature/
indoor coil
thermistor

3-time flash
Cause:
Indoor unit

• Trouble of
indoor fan
motor

6-time flash
Cause:
Outdoor unit

• Trouble of
thermistor
in outdoor
unit

7-time flash
Cause:
Outdoor unit

• Trouble of
outdoor
control
system

Check room
temperature
thermistor
and indoor
coil thermis­tor.
Refer to
"Test point
diagram and
voltage"
on page 25.

Refer to A
"Check of
indoor fan
motor"
on page 22.

MUH-A07/A09/A12YV
MXZ-A18/A26/A32WV

Refer to
"Check of
outdoor
thermistor"
and others.

MUH-A07/A09/A12YV
MXZ-A18/A26/A32WV

Replace the
deicer
P.C. board
and others.

MUH-A07/A09/A12YV
MXZ-A18/A26/A32WV

1-time flash
Cause:
Outdoor /
Indoor unit

• Trouble of
serial signal

Refer to D "How to check
mis-wiring and serial signal
error (When outdoor unit
doesn't work)" on page 24.
W1

1. Check indoor /
outdoor
connecting wire.

2. Refer to C
"Check of indoor
electronic control
P.C. board"
on page 23.

Outdoor unit
doesn't
stop even
if indoor unit
stops.

Unit doesn't
operate
normal
operation in
COOL or
HEAT mode.

MU-A07/A09/A12YV

Check of wiring
diagram of
outdoor unit".

MUH-A07/A09/A12YV

Refer to
"Check of
outdoor unit".

MUH-A07/A09/A12YV
MXZ-A18/A26/A32WV

Refer to
"Check of
R.V. coil" and
others.

W1.<The case of the trouble of the serial signal>
When the power is turned off and then turned on again, the indication shows “the trouble of mis-wiring”.

As for outdoor unit MU type, refer to service manual OB330.
As for outdoor unit MUH type, refer to service manual OB331.
As for outdoor unit MUX type, refer to service manual OB307 REVISED EDITION-A or OB318.
As for outdoor unit MXZ type, refer to service manual OB319.

Indoor unit
operates.
But indoor
unit doesn't
blow out
cool air.

MUX-A10/A19/A20/
A22/A25/A26WV

Refer to
"Check of
indoor/outdoor
units' connection
and outdoor
unit".

10-time flash
Cause:
Outdoor unit

MXZ type

• Outdoor
refrigerant
system
abnormality

MXZ type

Refer to
outdoor
refrigerant
system
related items.

MXZ type

5-time flash
Cause:
Outdoor unit

• Outdoor
power
system
abnormality

Refer to
"Check of
inverter/
compressor"
and "Check
of power
supply".

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20

Operation Indicator

· Flashing of the OPERATION INDICATOR lamp (on the left-hand side) indicates possible abnormalities.

· The OPERATION INDICATOR lamp (on the left-hand side) is lighting during normal operation.

flashing

• The following indication does not depend on the shape of lamp.

No.

1

2

4

6

7

SymptomOperation indicator lamp Detection method

Checkpoint

0.5-second ON

0.5-second OFF

MUH or
MXZ type

Mis-wiring

MUH or
MXZ type

Defrost
thermistor

MUH or
MXZ type

Outdoor
control
system
error

When serial signal stops for 4 to 5 seconds af­ter 1st on of 52C relay by POWER turning on.

When the defrost thermistor shorts or opens
after the compressor start-up.

When it cannot properly read data in the non­volatile memory of outdoor electronic control
P.C. board.

When the operation mode of each indoor unit
is differently set to COOL(includes DRY) and
HEAT at same time, the operation mode of
indoor unit that has operated at first has the
priority.

● Check outdoor DEICER P.C.
board and others.

● Check resistance of
thermistor.

● Reconnect connector.
Refer to service manual
OB331 or OB319.

● Check outdoor DEICER P.C.
board and others.

Refer to service manual

OB331 or OB319.

● Unify the operation mode.

● Check switch SW2-2.(MU &

MUX type or MUH & MXZ
type)

● Check wiring (visual check
and conductivity check).

● Check indoor electronic
control P.C.board.

● Check outdoor DEICER P.C.
board and others.

● Check electrical parts.

● Check resistance of

thermistor.

● Reconnect connector.

● Check indoor electronic

control P.C.board.

3

Indoor coil
thermistor

Room
temperature
thermistor

8

MXZ type

Outdoor
refrigerant
system
error

When the compressor operation has been in­terrupted by LEV protection continuously 5
minutes, the compressor stops operation.

Abnormal

point

Outdoor unit
does not run.

Outdoor unit
does not run.

Outdoor unit
does not run.

Outdoor unit
does not run.

Outdoor unit
does not run.

Outdoor unit
does not run.

MUH or
MXZ type

Serial
signal

1-time flash

2.5-second OFF

2-time flash

2.5-second OFF

When serial signal from outdoor unit stops for
4 to 5 seconds.

Detect Indoor coil/room temperature thermis­tor short or open circuit every 8 seconds dur­ing operation.

3-time flash

2.5-second OFF

Indoor fan motor
repeats 12 sec­onds ON and 3
minutes OFF.
When the indoor
fan motor
breaks, the fan
keeps stopping.

When rotational frequency feedback pulse
signal is not emit during 12-second indoor fan
operation.

When the compressor operation is
continuously three times interrupted by over
current protection within 1 minute after start­up , it stops operation.

● Disconnect connector
CN211 and then check
connector CN121 2-3 to
make sure rotational
frequency feedback signal of

1.5V or over exists.

● Check indoor electronic
control P.C. board.

● Check indoor fan motor.

● Reconnect connector.

● Check the inverter output.

● Check the compressor.

Indoor fan
motor

6-time flash

2.5-second OFF

● Refer to "Check of LEV".

● Check refrigerant circuit and

refrigerant amount.

● Check outdoor electronic
control P.C. board.
Refer to service manual
OB319.

5

5-time flash

2.5-second OFF

Operation Indicator

MXZ type

Operation
mode
setting

Lighted
Flashing

Outdoor unit
operates but
indoor unit
does not run.

7-time flash

2.5-second OFF

10-time flash

2.5-second OFF

MXZ type

Outdoor
power
system

2.5-second OFF

10-3. Troubleshooting check table

❈ Before taking measures, make sure that the symptom reappears, for accurate troubleshooting.
Self check table

21

10-4. Trouble criterion of main parts

RED

BLK

YLW

FUSE

GRY

BRN

WHT

RED

YLW
BRN

ORN

GRN

ROTOR

MSC-A07YV ­MSC-A09YV ­MSC-A12YV -

E1

E1

E1

Part name

Room
temperature
thermistor (RT11)

Indoor coil
thermistor (RT12)

Indoor fan
motor (MF)
INNER FUSE
136i3°C
CUT OFF

Vane motor
(MV)

Check method and criterion

Measure the resistance with a tester.
(Part temperature 10°C ~ 30°C)

Normal

MSC-A07/A09/A12YV

8kΩ ~ 20kΩ

Measure the resistance between the terminals with a tester.
(Coil wiring temperature10°C ~ 30°C)

Color of

lead wire

Motor partSensor part

BLK-RED

MSC-A07/A09YV

396 ~ 430ΩWHT-BLK
320 ~ 348Ω

Normal

MSC-A12YV

303 ~ 329Ω
287 ~ 311Ω

Measure the voltage Power ON.

Color of

lead wire

BRN-YLW

(When fan revolved one time)

YLW-GRY

Normal

MSC-A07/A09/A12YV

4.5 ~ 5.5V

0V➔5V➔0V

(Approx.)

Measure the resistance between the terminals with a tester.
(Part temperature10°C ~ 30°C)

Normal

MSC-A07/A09/A12YV

240 ~ 260Ω

Abnormal

Open or

short-circuit

Figure

Abnormal

Open or

short-circuit

Abnormal

Open or

short-circuit

Abnormal

Remain 0V or 5V

When OPERATION INDICATOR lamp flashes 3-time.

Indoor fan motor doesn’t operate.

AA

Check of indoor fan motor

Turn OFF the power supply.
Check connector CN211 visually.

No

Is resistance 0 (short circuit) or ∞ (open circuit)?

Are lead wires connected?

Repair or replace the indoor fan motor.

Reconnect the lead wires.

Disconnect lead wires from connector CN211 on indoor electronic control P.C. board.
Measure resistance between lead wires No.1 and No.5 and then No.3 and No.5.

Yes

Yes ( 0 or ∞ )

Yes

22

Is soldered point of the

connector correctly soldered?

Turn ON the power supply. Stop it if the unit operates.
Insert screwdriver into air outlet to rotate indoor fan
motor slowly for 1 revolution or over, and measure volt-

No

(others)

age No.2(+) and No.3(-) on CN121.

No

Does voltage repeat 0V DC and 5V DC?

Replace the indoor electronic control P.C. board.

No

Yes

Resolder it.

Indoor unit operates by pressing the EMERGENCY OPERATION switch, but doesn’t operate with the remote controller.

BB

Check of remote controller and receiver P.C. board

wCheck the remote controller is exclusive for this air conditioner.

Switch on the remote controller.

Is LCD display on the remote con­troller displayed?

No
(not clear)

Replace the batteries. (Refer to page 19.)

Yes

Remove batteries, then set them back and press the RESET
button. Check if the unit operates with the remote controller.

Does the unit operate with the
remote controller?

No

Turn on a radio to AM and press switch
on the remote controller.

Yes

OK

Measure the voltage between receiver P.C. board connector CN302

(–)

No.3

and No.5

(+)

when the remote controller button is pressed.

Replace the power monitor, receiver P.C. board.

Is noise heard from radio?

Yes

Are there any fluorescent lights of
inverter or rapid-start type within
the range of 1m?

No

Is the voltage approx. 4V DC?

No(5V or 0V DC)

No

Yes

Yes

Replace the remote controller.

• Reinstall the unit away from lights.

• Attach a filter on receiving part.

Replace the indoor electronic control
P.C. board.

The unit doesn’t operate with the remote controller.
Also, the OPERATION INDICATOR lamp doesn’t light up by pressing the EMERGENCY OPERATION switch.

CC

Check of indoor electronic control P.C. board

Check the both “parts side” and “pattern
side” of indoor electronic control P.C.
board visually.

Turn OFF the power supply.
Remove indoor fan motor connector CN211 and
vane motor connector CN151 from the indoor electronic
control P.C. board and turn ON the power supply.

Does the unit operate with the remote controller?
Does the OPERATION INDICATOR lamp light up
by pressing the EMERGENCY OPERATION switch?

Yes

Turn OFF the
power supply.

Be sure to check both resistances.

Replace the vane
motor.

Yes

Is winding
resistance of
vane motor 0 "?

Is winding
resistance of
fan motor 0 "?

Yes

Replace the fan motor.

Turn OFF the
power supply.

No

No

No

Be sure to check both fuse
and varistor in any case.

Replace the fuse.

Yes

Is fuse (F11) blown?

Is varistor (NR11) burnt?

Yes

Replace the varistor.

No

No

Replace the indoor
electronic control
P.C. board.

23

Mis-wiring is indicated.
(0.5-sec. ON, 0.5-sec. OFF)

1. Turn OFF the power supply(indoor / outdoor unit) and disconnect indoor and outdoor connecting wire on indoor side.

2. Short-circuit between indoor terminal block N and 3.

3. Turn ON the power supply(indoor unit) and press once EMERGENCY OPERATION switch.

During EMERGENCY OPERATION,
is there 10V DC between both ends
of R601?
(By tester, the stylus is between 5 ~10V)

Serial signal error is indicated.
(0.5-sec. ON, 2.5-sec. OFF)

Start

Turn OFF the power supply(indoor/outdoor unit).

No

No

Is there 20V DC between both ends of
R132 on indoor electronic control P.C.
board ?
( By tester, the stylus is between 0 ~ 20V. )

•Turn OFF the power supply(indoor unit).

•Connect ON indoor and outdoor connecting wire.

Is the outdoor unit "MUH" type?

•Turn ON the power supply(indoor/outdoor unit).

•Press once EMERGENCY OPERATION switch.

Is this mis-wiring, poor contact,
or disconnection of wire?

Make them sure.

Replace the indoor electronic
control P.C. board.

Turn ON the power supply(outdoor unit).

Is there 230V AC between outdoor terminal

block L-N (TB1)?

No

Check the outdoor power supply,
power supply cord and
connection.

Yes

Turn ON the power supply(indoor unit).

No

Replace the deicer P.C. board.

Yes

No

Make the wiring between CN730
on the deicer P.C. board and
outdoor terminal block correct.

Replace the deicer P.C. board.

Yes

Yes

Yes

3 min. later, what self-check result is
displayed on OPERATION INDICATOR
lamp on indoor unit?

w 2

Set the switch(SW2-2) on the indoor electronic
control P.C. board to MU or MUX type.

w1

Yes

Does the unit operate?

OK

Yes

No

No

Refer to the
"Instruction of
troubleshooting."

w 2 Short circuit of JPG and JPS on the indoor electronic control
P.C. board enables self-check to be displayed in 3 seconds.

w 1 Set the switch(SW2-2) on indoor electronic control P.C. board to

MU or MUX type, when the outdoor unit is MU or MUX type.
If the setting is MUH or MXZ type, the unit does not work.

Is there 5V DC between J205 + –J101 - on the deicer P.C. board?

As for outdoor unit MUH type, refer to service manual OB331.
As for outdoor unit MXZ type, refer to service manual OB319.

When OPERATION INDICATOR lamp flashes 0.5-second intervals or 1-time.
Outdoor unit does not operate.

DD

How to check mis-wiring and serial signal error

<MUH-A07/A09/A12YV, MXZ-A18/A26/A32WV>

24

TEST POINT DIAGRAM AND VOLTAGE

0

0

10

20

30

40

10 20 30 40 50 60

MSC-A07YV ­MSC-A09YV ­MSC-A12YV -

E1

E1

E1

Indoor electronic control P.C. board

Varistor
(NR11)

12V DC

--

{

+

Fuse 250V AC 3.15A

Indoor fan motor
230 V AC

}

Power supply input

}

230 V AC

R132

Indoor coil
thermistor (RT12)

Room temperature
thermistor (RT11)

Timer short mode
point JPG, JPS

}

(Refer to page 17.)

Emergency
operation switch

SW2

(Refer to page 18.)

1 sets the Auto restart

function ON/ OFF.

Power monitor,
receiver P.C. board

CN302

--+

}

2 switches over MU&MUX type/

5V DC

MUH & MXZ type.

Indoor coil thermistor (RT12)
Room temperature thermistor (RT11)

)

''

25

Resistance (k

Temperature (;;)

11

DISASSEMBLY INSTRUCTIONS

<"Terminal with lock mechanism" Detaching points>

In case of terminal with lock mechanism, detach the terminal as shown below.
There are two types ( Refer to (1) and (2)) of the terminal with lock mechanism.
The terminal with no lock mechanism can be removed by pulling it out.
Check the shape of the terminal and work.

(1) Slide the sleeve and check if there is a locking lever or not. (2) The terminal with this connector is a terminal

Sleeve

with lock mechanism

1Slide the sleeve.
2Pull the terminal while

Locking lever

pushing the locking
lever.

MSC-A07YV - MSC-A09YV - MSC-A12YV ­INDOOR UNIT

OPERATING PROCEDURE PHOTOS

1. Removing the front panel

(1) Remove the screw caps of the front panel.

Remove the screws.

(2) Pull the panel down to your side slightly and unhook the

catches at the top.

1Hold the sleeve, and
pull out the terminal
slowly.

Connector

E1E1E1

Photo 1

Screws of the front panel

2. Removing the electronic control P.C. board and the
power monitor, receiver P.C. board

NOTE : In case of removing only indoor electronic control

P.C. board, work (3) is not necessary.
(1) Remove the front panel. (Refer to 1.)
(2) Remove the power monitor, receiver P.C. board holder

from the bottom of electrical box.

(3) Open the power monitor, receiver P.C. board holder and

remove the power monitor, receiver P.C. board.

(4) Remove the screw of the electrical cover and the electrical

cover.
(5) Remove the screw of the V.A. clamp and the V.A. clamp.
(6) Remove the screw of the cord clamp and the cord clamp.
(7) Remove the screw of the terminal block.
(8) Remove the screw of the ground wire.
(9) Pull out indoor electronic control P.C. board slightly.
(10)

Disconnect all (except CN101) the connectors on the elec-

tronic control P.C. board.
(11)

Remove the electronic control P.C. board.

(12)

Disconnect the connector of power monitor, receiver P.C.

board (CN101) on the electronic control P.C. board.

Photo 2

Screw of the
ground wire

Power monitor, receiver
P.C. board holder

Terminal block
fixing screw

Indoor electronic
control P.C. board

Cord clamp fixing
screw

Screw of the V.A.
clamp

Screw of the
electrical cover

26

OPERATING PROCEDURE

PHOTOS

3. Removing the electrical box

(1) Remove the front panel. (Refer to 1.)
(2) Remove the electrical cover. (Refer to 2.)
(3) Remove the V.A. clamp. (Refer to 2.)
(4) Remove the cord clamp. (Refer to 2.)
(5) Remove the terminal block. (Refer to 2.)
(6) Remove the screw of ground wire. (Refer to 2.)
(7) Disconnect the connector of the indoor coil thermistor

(CN112), the fan motor connector (CN211 and CN121) and
the vane motor connector (CN151) on the electronic con­trol P.C. board.

(8) Remove the fan motor lead wire and indoor coil thermistor

from the electrical box.

(9) Remove the lead wire of vane motor from the bottom of

electrical box.

(10)

Remove the screw fixing the electrical box, remove the

electrical box.

4. Removing the nozzle assembly and the vane motor

(1) Remove the front panel. (Refer to 1.)
(2) Remove the electrical box. (Refer to 3.)
(3) Pull out the drain hose from the nozzle assembly, remove

the nozzle assembly.

(4) Remove the screws of the vane motor, disconnect the

vane motor connector.

(5) Remove the vane motor.

Photo 3

Photo 4

Indoor coil thermistor
connector

Fan motor connector

Screws of the vane motor

Vane motor
connector

Screw of the
electrical box

5. Removing the indoor fan motor and the line flow fan

(1) Remove the front panel. (Refer to 1.)
(2) Remove the electrical box. (Refer to 3.)
(3) Pull out the drain hose from the nozzle assembly, remove

the nozzle assembly. (Refer to 4.)
(4) Remove the screw of the lead cover and lead cover.
(5) Release the hooks to open the motor band slightly.
(6) Loosen the hexagon socket set screw from the line flow

fan.
(7) Remove the screws fixing the motor bed, remove the fan

motor with motor band and the motor bed.
(8) Remove the screws fixing the left side of the heat

exchanger.
(9) Lift the left side of the heat exchanger.
(10)

Remove the line flow fan.

Photo 6

Screw of
the lead
cover

Hexagon socket set screw

Hooks of the
motor band

Drain hose

Photo 5

Screws of the

left side of the
heat exchanger

Photo 7

Screws of
the motor
bed

27

12

1
2

3
4
5

6
7

8
9

E02 749 234
E02 751 234
E02 829 000
E02 749 067
E02 829 010
E02 408 142
E02 763 100
E02 764 100

E02 749 975
E02 408 970
E02 751 970

BOX(WH)
BOX(WH)
PANEL ASSEMBLY(WH)
SCREW CAP(WH)
FRONT PANEL(WH)
CATCH
CATECHIN AIR FIL TER
CATECHIN AIR FIL TER
AIR CLEANING FILTER
CORNER BOX (RIGHT)
INSTALLATION PLATE
INSTALLATION PLATE

Symbol

in Wiring

Diagram

Q'ty/unit

1

1
2
1
2
2

2
1
1

Including No.3,4,5
2PCS/SET

2PCS/SET

MAC-1300FT

Remarks

Part No.

No.

Part Name

MSC-A07YV-

E1 (WH)

1
1
2
1
2

2
2
1

1

1

1
2
1
2
2

2
1
1

1
1

1
1

1
1

E02 749 426
E02 527 083

10
11

REMOTE CONTROLLER
REMOTE CONTROLLER HOLDER

MSC-A09YV-

E1 (WH)

MSC-A12YV-

E1 (WH)

PARTS LIST

MSC-A07YV - (WH)
MSC-A09YV - (WH)
MSC-A12YV - (WH)

E1

E1

E1

12-1. INDOOR UNIT STRUCTURAL PARTS

1 (W)

2

3

4

5

6 (W)

12-2. ACCESSORY AND

9 (W)

8

7 (See page 30.)

(W) These figures show about MSC-A12YV.

REMOTE CONTROLLER

10

11

12-1. INDOOR UNIT STRUCTURAL PARTS

12-2. ACCESSORY AND REMOTE CONTROLLER

28

MSC-A07YV - (WH) MSC-A09YV - (WH) MSC-A12YV - (WH)

E1E1E1

12-3. INDOOR UNIT ELECTRICAL PARTS

12-4. INDOOR UNIT HEAT EXCHANGER

AND FUNCTIONAL PARTS

SLEEVE
BEARING

1
3

4

5

19

18

2

FUSE

VARISTOR

6

17

14

7

11

16

ROOM TEMPERATURE
THERMISTOR

12

13

10

9

8

15

22
23

(W) This figure shows about MSC-A12YV.

12-3. INDOOR UNIT ELECTRICAL PARTS AND FUNCTIONAL PARTS

Part number that is circled is not shown in the illustration.

Q'ty/unit

MSC-A09YV-

E1 (WH)

1
1
1
1
1
1
1
1
1

1

1
1
1

1
1
2

1
1
1

1

No.

E02 001 504

1

E02 661 702

2

E02 749 235

3

E02 749 040

4

E02 749 041

5

E02 127 382

6

E02 829 385

7

E02 763 034

8

E02 749 468

9

E02 829 452
E02 830 452

10

E02 831 452
E02 749 303

11

E02 151 308

12

E02 749 300

13

E02 751 300
E02 749 333

14

E02 691 375

15

E02 665 505

16

E02 151 505
E02 749 307

17
18

E02 749 302
E02 408 509

19

E02 751 509
E02 749 385

20

Part No.

Symbol

Part Name

SLEEVE BEARING
DRAIN HOSE
NOZZLE ASSEMBL Y(WH)
VANE UPPER (WH)
VANE LOWER (WH)
FUSE
VARISTOR
VANE CRANK SET
POWER MONITOR, RECEIVER P.C. BOARD
ELECTRONIC CONTROL P.C.BOARD
ELECTRONIC CONTROL P.C.BOARD
ELECTRONIC CONTROL P.C.BOARD
VANE MOTOR
ROOM TEMPERATURE THERMISTOR
INDOOR FAN MOTOR
INDOOR FAN MOTOR
MOTOR BAND
TERMINAL BLOCK
FAN MOTOR RUBBER MOUNT
FAN MOTOR RUBBER MOUNT
INDOOR COIL THERMISTOR
LINE FLOW FAN
BEARING MOUNT
BEARING MOUNT
VARISTOR

in Wiring

Diagram

NR12

F11

NR11

MV

RT11

MF
MF

TB

RT12

MSC-A07YV-

E1 (WH)

1
1
1
1
1
1
1
1
1
1

1
1
1

1
1
2

1
1
1

1

21 (W)

MSC-A12YV-

E1 (WH)

1
1
1
1
1
1
1
1
1

1
1
1

1
1
1

2
1
1

1
1

Remarks

3.15A

AUTO RESTART
AUTO RESTART
AUTO RESTART

RC4V19­RC4V19-

2PCS/SET
2PCS/SET

12-4. INDOOR UNIT HEAT EXCHANGER

E02 749 620

21

E02 751 620
E02 151 666

22

E02 155 666

23

E02 151 667

INDOOR HEAT EXCHANGER
INDOOR HEAT EXCHANGER
UNION(GAS)
UNION(GAS)
UNION(LIQUID)

29

1

1

1

1

1

1

1

1

1

{9.52
{12.7
{6.35

Air cleaning filter
(White bellows type)

12-5. AIR CLEANING FILTER

Model

Part No.

MAC-1300FT

MSC-A07YV­MSC-A09YV­MSC-A12YV-

E1
E1

E1

● AIR CLEANING FILTER removes fine dust of 0.01 micron from air by means of static electricity.

● Normal life of AIR CLEANING FILTER is 4 months. However, when it becomes dirty, replace it as soon as possible.

● Clogged AIR CLEANING FILTER may reduce the air conditioner capacity or cause frost on the air outlet.

● DO NOT reuse AIR CLEANING FILTER even if it is washed.

● DO NOT remove or attach AIR CLEANING FILTER during unit operation.

30

HEAD OFFICE: MITSUBISHI DENKI BLDG.,2-2-3, MARUNOUCHI, CHIYODA-KU, TOKYO100-8310, JAPAN

CC

Copyright 2003 MITSUBISHI ELECTRIC ENGINEERING CO.,LTD
Distributed in Dec. 2003. No.OB329 6
Made in Japan

New publication, effective Dec. 2003
Specifications subject to change without notice.