Mitsubishi Electric MSC-GA20VB- E1 User manual

SERVICE MANUAL
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. SERVICE FUNCTIONS ······································9
9. TROUBLESHOOTING······································11
10. DISASSEMBLY INSTRUCTIONS·····················18
11. PARTS LIST······················································20
12. OPTIONAL PARTS···········································22
Wireless type
Models
MSC-GA20VB - (WH)
MSC-GA25VB - (WH)
MSC-GA35VB - (WH)
E1
E1
E1
MSC-GA20VB -
MSC-GA25VB -
MSC-GA35VB - E1
E1
E1
No. OB385
SPLIT-TYPE, AIR CONDITIONERS
SPLIT-TYPE, HEAT PUMPAIR CONDITIONERS
Indication of model name
NOTE:
•This manual describes technical data of indoor units.
•As for outdoor units MU-GA20/GA25/GA35VB - , refer to the service manual OB386.
•As for outdoor units MUH-GA20/GA25/GA35VB - , refer to the service manual OB387.
•As for outdoor units MUX-2A28/2A59/3A60/3A63/2A70/4A73VB - , refer to the service manual
OB384.
•As for outdoor units MXZ-A14/A18/A26/A32WV - , refer to the service manual OB319 REVISED
EDITION-A. E1
E1
E1
E1
OB385-1.qxp 05.1.25 18:50 Page 1

2
OB385-1.qxp 05.1.25 14:50 Page 2

3
PART NAMES AND FUNCTIONS
2
INDOOR UNIT
MSC-GA20VB - MSC-GA25VB - MSC-GA35VB - E1E1E1
Emergency operation switch
Fan
Catechin air filter
(With deodorizer)
Air outlet
Vertical vanes
Air inlet
to Breaker
Remote control
receiving section
Display section
Air cleaning filter(option)
(white bellows type) Front panel
Power supply cord
Panel
Horizontal vane
Operation section
(When the front panel is opened)
Remote controller
Operation indicator lamp
Remote control
receiving section
TECHNICAL CHANGES
1
MSC-A07YV - ➔ MSC-GA20VB -
1. Indication of capacity has been changed. (BTU base ➔ kW)
2. P.C. board has been changed.
3. Air cleaning filter has been changed to optional parts.
4. Fan motor has been changed.
5. Fan motor capacitor has been changed.
6. Color of indoor unit has been changed.
MSC-A09YV - ➔ MSC-GA25VB -
1. Indication of capacity has been changed. (BTU base ➔ kW)
2. P.C. board has been changed.
3. Air cleaning filter has been changed to optional parts.
4. Fan motor has been changed.
5. Fan motor capacitor has been changed.
6. Color of indoor unit has been changed.
MSC-A12YV - ➔ MSC-GA35VB -
1. Indication of capacity has been changed. (BTU base ➔ kW)
2. P.C. board has been changed.
3. Air cleaning filter has been changed to optional parts.
4. Fan motor has been changed.
5. Fan motor capacitor has been changed.
6. Color of indoor unit has been changed.
E1E1
E1E1
E1E1
OB385-1.qxp 05.1.26 12:34 Page 3

4
ACCESSORIES
MSC-GA20VB -
MSC-GA25VB -
MSC-GA35VB - E1
E1
E1
Installation plate
Installation plate fixing screw 4 o25 mm
Remote controller holder
Fixing screw for 33.5 o16 mm
Battery (AAA) for remote controller
Wireless remote controller
Felt tape (Used for left or left-rear piping)
1
5
1
2
2
1
1
<Indoor unit>
1
2
3
4
5
6
7
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
REMOTE CONTROLLER
OB385-1.qxp 05.1.25 14:50 Page 4

5
SPECIFICATION
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-GA20VB - E1
Single phase
230V,50Hz
10
0.17
35
90
0.17
RC4V19-JA
WHT-BLK 283
BLK-RED 188
815O278O244
9
5
3
10
10
KP1A
Cooling
474/372 /276
36/31 /25
900/750 /600
Heating
510/420 /342
36/31 /25
950/820 /700
MSC-GA25VB - E1
Single phase
230V,50Hz
10
0.17
35
90
0.17
RC4V19-JA
WHT-BLK 283
BLK-RED 188
815O278O244
9
5
3
10
10
KP1A
Cooling
474/384 /306
36/31 /25
900/770 /650
Heating
588/456 /342
39/32 /25
1,050/870 /700
MSC-GA35VB - E1
Single phase
230V,50Hz
10
0.19
40
92
0.19
RC4V19-HA
WHT-BLK 224
BLK-RED 318
815O278O244
10
5
3
10
10
KP1A
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
w w
w w
wwwwwwwwww
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w
wwww
NOTE: 1. Test conditions are based on ISO 5151.
Cooling : Indoor DB27°C WB19°C Heating : Indoor DB20°C
Outdoor DB35°C WB24°C Outdoor DB7°C WB6°C
Indoor-Outdoor piping length 5m
WReference value
OB385-1.qxp 05.1.25 18:50 Page 5

6
NOISE CRITERIA CURVES
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-GA20VB- E1 COOLING
High
FUNCTIONFAN SPEED
36
HEATING
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-GA25VB- E1 COOLING
High
FUNCTIONFAN SPEED
36
HEATING 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:
Heating : DB20:WB -:
MSC-GA35VB- E1 COOLING
FUNCTIONFAN SPEED
40
HEATING
High 39
SPL(dB(A)) LINE
INDOORUNIT WALL
MICROPHONE
0.8m
1m
OB385-1.qxp 05.1.25 14:50 Page 6

7
OUTLINES AND DIMENSIONS
5
MSC-GA20VB -
MSC-GA25VB - E1
E1
INDOOR UNIT
244
242 5
7 or more
90
110
30
149
606
278
60
815
783
Power supply cord
Lead to right 1.0m
Lead to left 0.3m
Air out
Installation plate
Insulation [28
Drain hose [16
(Connected part O,D)
Air in
Liquid line [6.35-0.5m
Gas line [9.52-0.43m
Insulation [37 O.D
[21 I.D
{
Wireless remote controller
162
19
58
81.5
81.5
41
2.5
42
271
231.5
4.5
81.5 133.5
326326
Wall hole [65
Indoor unit
Installation plate
Unit: mm
MSC-GA35VB - E1
INDOOR UNIT
244
242
218.5
258
81.581.5
41
42
2.5
17.5
161.5161.5
326326
5
7 or more
90
110
30
149
606
278
60
815
783
Power supply cord
Lead to right 1.0m
Lead to left 0.3m
Air out
Indoor unit
Installation plate
Wall hole [65
Installation plate
Insulation [28
Drain hose [16
(Connected part O,D)
Liquid line [6.35-0.5m
Gas line [9.52-0.43m
Insulation [37 O.D
[21 I.D
{
Wireless remote controller
162
19
58
Air in
OB385-1.qxp 05.1.25 14:50 Page 7

8
REFRIGERANT SYSTEM DIAGRAM
7
MSC-GA20VB - MSC-GA25VB - MSC-GA35VB - E1E1E1
INDOOR UNIT
Indoor
heat
exchanger
Room temperature
thermistor
RT11
Refrigerant pipe [9.52
(with heat insulator) Unit:mm
Indoor coil
thermistor
RT12
Flared connection
Flared connection
WIRING DIAGRAM
6
MSC-GA20VB - MSC-GA25VB - MSC-GA35VB - E1E1E1
MODELS WIRING DIAGRAM
SYMBOL
NR11
RT11
RT12
SR141
NAME NAME NAME
INDOOR FAN CAPACITOR
FUSE(3.15A)
INDOOR FAN MOTOR (INNER FUSE)
VANE MOTOR
VARISTOR
ROOM TEMPERATURE THERMISTOR
INDOOR COIL THERMISTOR
SOLID STATE RELAY
TERMINAL BLOCK
SYMBOL
C11
F11
MF
MV
SYMBOL
TB
T11 TRANSFORMER
MF
1
2
3
4
5
6
125
CNCN
109
5
REMOTE
CONTROLLER
23
POWER MONITOR
RECEIVER P.C.BOARD
GRN
LD103
PE
12V
FOR
MU OR
MUX TYPE
FOR MUH OR
MXZ-A TYPE
MV
GRN/YLW
POWER
SUPPLY
CORD
~/N 230V
50Hz
TO OUTDOOR
UNIT
CONNECTING
12V
1
2
N
3
LBRN
BLU
BLK
WHT
BLU
RED
BRN
5
CN
151
1
2
CN202
1
2
3
CN201
LD105
CN211
ELECTRONIC CONTROL P.C. BOARD
F11
T11
NR11
RT11
RT12
CN
112
CN
111
5
3
1
CN
121
BLK
GRY
YLW
BRN
3
WHT
RED
C11
SR141
CIRCUIT BREAKER
TB
INDOOR UNIT
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
Refrigerant pipe [6.35
(with heat insulator)
Refrigerant flow
in cooling
OB385-1.qxp 05.1.25 14:50 Page 8

9
SERVICE FUNCTIONS
8
8-2. 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.
8-1. 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 9-6.)
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.)
How to modify the remote controller P.C. board
Remove batteries before modification. The board has a print as shown below :
NOTE : For remodelling, take out the
batteries and press the
OPERATE/STOP(ON/OFF)
button twice or 3 times at first.
After finish remodelling, put
back the batteries then press
the RESET button.
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.
Table 1
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
MSC-GA20VB -
MSC-GA25VB -
MSC-GA35VB - E1
E1
E1
Remote controller model : KP1A J2
J1
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.
Slide switch Type
The position
of the slide
switch
COOL ONLYCOOL & HEAT
8-3. 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.
OB385-1.qxp 05.1.25 14:50 Page 9

10
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.
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 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.
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
}
SW2
FRONT
12
12
IC101
CN151
SW1
CN112
CN121
L101
CN201
F11
CN202
C11
CN211
SW2
LD105
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.)
8-4. MU & MUX TYPE / MUH & MXZ TYPE SWITCH OVER AND AUTO RESTART FUNCTION
2. AUTO RESTART FUNCTION
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 opera-
tion is decided by the initial room temperature. “AUTO RESTART FUNCTION” is ON when the units are shipped from
the factory.
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.
NOTE:•If the indoor-outdoor connecting wire is incorrectly
connected on the terminal block, the unit does not
operate normally.
•If a ground is incorrect, it may cause an electric shock.
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.
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.
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11
TROUBLESHOOTING
9
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 9-2. “Instruction of troubleshooting” and 9-3. “Troubleshooting check table”.
Lead wiring Housing point
9-1. 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 turn off the main unit first with the remote controller, and then after con-
firming 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.
MSC-GA20VB -
MSC-GA25VB -
MSC-GA35VB - E1
E1
E1
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.
NOTE1 : If the RESET button is not pressed, the remote controller may not operate correctly.
Insert the negative pole
of the batteries first.
Check if the polarity of
the batteries are correct.
HEAT
/FAN
/
RESET button
HEAT
/FAN
/
1Remove the front lid and insert batteries.
Then reattach the front lid.
2Press the RESET button.
NOTE2 : INFORMATION FOR MULTI SYSTEM AIR CONDITIONER
(OUTDOOR UNIT : MXZ-A14WV- MXZ-A18WV- MXZ-A26WV- MXZ-A32WV- )
Multi system air conditioner (Outdoor unit MXZ-A14WV- 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.
•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.
E1E1E1E1
E1E1E1E1
lighted
flashing
Operation Indicator
OB385-1.qxp 05.1.25 14:50 Page 11

12
9-2. 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 9-6.
"Test point
diagram and
voltage".
MUH-GA20/GA25/GA35VB
MUX-2A28/2A59/3A60/
3A63/2A70/4A73VB
Refer to
"Check of
outdoor unit".
Refer to 9-5.
B"Check of
remote
controller
and receiver
P.C. board".
MUH-GA20/GA25/GA35VB
MXZ-A14/A18/A26/A32WV
Flash on and off at
0.5-second intervals
Cause:
Indoor/Outdoor unit
• Mis-wiring or
trouble of serial signal
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 thermis-
tor.
Refer to 9-6.
"Test point
diagram and
voltage".
Refer to 9-5.
A"Check of
indoor fan
motor".
4-time flash
Cause:
Indoor unit
• Trouble of
indoor unit
control
system
Replace the
indoor
electronic
control
P.C. board.
MUH-GA20/GA25/GA35VB
MXZ-A14/A18/A26/A32WV
Refer to
"Check of
outdoor
thermistor"
and others.
MUH-GA20/GA25/GA35VB
MXZ-A14/A18/A26/A32WV
Replace the
deicer
P.C. board
and others.
Refer to 9-5. D "How to
check mis-wiring and serial
signal error (When outdoor
unit doesn't work)".
W1
1. Check indoor /
outdoor
connecting wire.
2. Refer to 9-5. C
"Check of indoor
electronic control
P.C. board".
Outdoor unit
doesn't
stop even
if indoor unit
stops.
Unit doesn't
operate
normal
operation in
COOL or
HEAT mode.
MU-GA20/GA25/GA35VB
Check of wiring
diagram of
outdoor unit".
MUH-GA20/GA25/GA35VB
Refer to
"Check of
outdoor unit".
MUH-GA20/GA25/GA35VB
MXZ-A14/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 OB386.
As for outdoor unit MUH type, refer to service manual OB387.
As for outdoor unit MUX type, refer to service manual OB384.
As for outdoor unit MXZ type, refer to service manual OB319 REVISED EDITION-A.
Indoor unit
operates.
But indoor
unit doesn't
blow out
cool air.
MUX-2A28/2A59/3A60/
3A63/2A70/4A73VB
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".
MSC-GA20VB -
MSC-GA25VB -
MSC-GA35VB - E1
E1
E1
OB385-1.qxp 05.1.25 14:50 Page 12

13
9-3. Troubleshooting check table
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.
❈ Before taking measures, make sure that the symptom reappears, for accurate troubleshooting.
Self check table
No.
1
2
5
7
8
SymptomOperation indicator lamp Detection method
Checkpoint
0.5-second ON
0.5-second OFF
MUH or
MXZ type
Mis-wiring
or Serial
signal
MUH or
MXZ type
Defrost
thermistor
MUH or
MXZ type
Outdoor
control
system
error
When the defrost thermistor shorts or opens
after the compressor start-up.
When it cannot properly read data in the non-
volatile 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
OB387 or OB319 REVISED
EDITION-A.
●Check outdoor DEICER P.C.
board and others.
Refer to service manual
OB387 or OB319 REVISED
EDITION-A.
●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
9
MXZ type
Outdoor
refrigerant
system
error
When the compressor operation has been in-
terrupted 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.
2-time flash
2.5-second OFF
When serial signal from outdoor unit stops for
4 to 5 seconds.
Detect Indoor coil/room temperature thermis-
tor short or open circuit every 8 seconds dur-
ing operation.
3-time flash
2.5-second OFF
Indoor fan motor
repeats 12 sec-
onds 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 start-
up , 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 REVISED
EDITION-A.
6
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.
4
4-time flash
2.5-second OFF
Indoor
control
system
When it cannot properly read data in the
nonvolatile memory of indoor electronic
control P.C. board.
Outdoor unit
does not
operate. ●Replace the indoor electronic
control P.C. board.
7-time flash
2.5-second OFF
10-time flash
2.5-second OFF
MXZ type
Outdoor
power
system
2.5-second OFF
OB385-1.qxp 05.1.25 14:50 Page 13

14
AACheck of indoor fan motor
Is soldered point of the
connector correctly soldered?
Is resistance 0 (short circuit) or ∞(open circuit)?
Yes ( 0 or ∞)
Yes
No
Yes
No
Turn OFF the power supply.
Check connector CN211 visually.
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.
When OPERATION INDICATOR lamp flashes 3-time.
Indoor fan motor doesn’t operate.
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-
age No.2(+) and No.3(-) on CN121.
No
(others)
Replace the indoor electronic control P.C. board.
Does voltage repeat 0V DC and 5V DC?
Yes
No
Are lead wires connected?
Reconnect the lead wires. Resolder it.
Repair or replace the indoor fan motor.
Measure the resistance between the terminals with a tester.
(Coil wiring temperature10°C ~ 30°C)
Room
temperature
thermistor (RT11)
9-4. Trouble criterion of main parts
Part name
Indoor coil
thermistor (RT12)
Indoor fan
motor (MF)
INNER FUSE
136i3°C
CUT OFF
Motor partSensor part
Check method and criterion
Measure the resistance with a tester.
(Part temperature 10°C ~ 30°C)
Measure the voltage Power ON.
Figure
8kΩ~ 20kΩ
Normal Abnormal
Open or
short-circuit
271 ~ 295ΩWHT-BLK
BLK-RED
BRN-YLW
YLW-GRY
Normal
4.5 ~ 5.5V
Abnormal
Remain 0V or 5V
(When fan revolved one time)
0V➔5V➔0V
(Approx.)
MSC-GA20/GA25VB
180 ~ 196Ω
RED
BLK
YLW
FUSE
GRY
BRN
WHT
MSC-GA20VB -
MSC-GA25VB -
MSC-GA35VB - E1
E1
E1
Normal Abnormal
Open or
short-circuit
MSC-GA20/GA25/GA35VB
MSC-GA20/GA25/GA35VB
Vane motor
(MV)
Measure the resistance between the terminals with a tester.
(Part temperature10°C ~ 30°C)
Normal Abnormal
Open or
short-circuit
240 ~ 260Ω
RED
YLW
BRN
ORN GRN
ROTOR
MSC-GA20/GA25/GA35VB
Color of
lead wire
215 ~ 233Ω
MSC-GA35VB
305 ~ 331Ω
Color of
lead wire
9-5. Troubleshooting flow
OB385-1.qxp 05.1.25 14:50 Page 14

15
BBCheck of remote controller and receiver P.C. board
Indoor unit operates by pressing the EMERGENCY OPERATION switch, but doesn’t operate with the remote controller.
Yes
Replace the batteries. (Refer to 9-1-4.)
Turn on a radio to AM and press switch
on the remote controller.
Is noise heard from radio?
Are there any fluorescent lights of
inverter or rapid-start type within
the range of 1m?
Replace the remote controller.
• Reinstall the unit away from lights.
• Attach a filter on receiving part.
Switch on the remote controller.
Is LCD display on the remote con-
troller displayed?
Remove batteries, then set them back and press the RESET
button. Check if the unit operates with the remote controller.
Yes
Does the unit operate with the
remote controller?
Yes
OK
No
(not clear)
Yes
No
No
Yes
Measure the voltage between receiver P.C. board connector CN302
No.3(–) and No.5(+) when the remote controller button is pressed.
Is the voltage approx. 4V DC? Replace the indoor electronic control
P.C. board.
Replace the power monitor, receiver P.C. board.
No(5V or 0V DC)
No
wCheck the remote controller is exclusive for this air conditioner.
CCCheck of indoor electronic control P.C. board
Check the both “parts side” and “pattern
side” of indoor electronic control P.C.
board visually.
Replace the fuse.
Is fuse (F11) blown?
Be sure to check both fuse
and varistor in any case.
Replace the fan motor.
Replace the indoor
electronic control
P.C. board.
Is winding
resistance of
fan motor 0 "?
Is winding
resistance of
vane motor 0 "?
No
Yes
Replace the vane
motor.
No
Yes
Yes
Is varistor (NR11) burnt?
Replace the varistor.
Yes
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.
No
Does the unit operate with the remote controller?
Does the OPERATION INDICATOR lamp light up
by pressing the EMERGENCY OPERATION switch?
Yes
No
Be sure to check both resistances.
Turn OFF the
power supply. Turn OFF the
power supply.
No
The unit doesn’t operate with the remote controller.
Also, the OPERATION INDICATOR lamp doesn’t light up by pressing the EMERGENCY OPERATION switch.
OB385-1.qxp 05.1.25 14:50 Page 15

16
DDHow to check mis-wiring and serial signal error
Serial signal error 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)
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.
•3 min. later, check the self-check result
displayed on OPERATION INDICATOR
lamp on indoor unit. w 2
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
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."
w2 Short circuit of JPG and JPS on the indoor electronic control
P.C. board enables self-check to be displayed in 3 seconds.
w1 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 OB387.
As for outdoor unit MXZ type, refer to service manual OB319 REVISED EDITION-A.
When OPERATION INDICATOR lamp flashes 0.5-second intervals or 1-time.
Outdoor unit does not operate.
<MUH-GA20/GA25/GA35VB, MXZ-A14/A18/A26/A32WV>
OB385-1.qxp 05.1.25 14:50 Page 16

17
MSC-GA20VB -
MSC-GA25VB -
MSC-GA35VB -
Indoor electronic control P.C. board
E1
E1
E1
CN302
Indoor coil thermistor (RT12)
Room temperature thermistor (RT11)
Temperature (:)
Resistance (k")
SW2
(Refer to 8-4.)
1sets the Auto restart
function ON/OFF.
2switches over MU&MUX type/
MUH & MXZ type.
Power supply input
230V AC
Varistor
(NR11)
Fuse F11 250V AC 3.15A
Room temperature
thermistor RT11
Indoor coil
thermistor
RT12
Timer short mode
point JPG, JPS
(Refer to 8-1.)
Emergency
operation switch
}
}
Indoor fan motor
230V AC
}
5V DC
+
–
{
12V
DC +
–
}
Safety device of
fan by horizontal
vane CN1R1
R132
J23
J33
J33
J12
Power monitor,
receiver P.C. board
9-6. Test point diagram and voltage
OB385-1.qxp 05.1.25 14:50 Page 17

18
DISASSEMBLY INSTRUCTIONS
10
MSC-GA20VB - MSC-GA25VB - MSC-GA35VB -
INDOOR UNIT E1E1E1
(1) Slide the sleeve and check if there is a locking lever or not. (2) The terminal with this connector has the locking
mechanism.
1Slide the sleeve.
2Pull the terminal while
pushing the locking
lever.
1Hold the sleeve, and
pull out the terminal
slowly.
The terminal which has the locking mechanism can be detached as shown below.
There are two types ( Refer to (1) and (2)) of the terminal with locking mechanism.
The terminal without locking mechanism can be detached by pulling it out.
Check the shape of the terminal before detaching.
<"Terminal with locking mechanism" Detaching points>
Connector
Sleeve
Locking lever
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.
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
Photo 1
Terminal block
fixing screw
Screw of the V.A.
clamp
Indoor electronic
control P.C. board
Screws of the front panel
Screw of the
ground wire
Power monitor, receiver
P.C. board holder
Screw of the
electrical cover
Cord clamp fixing
screw
OB385-1.qxp 05.1.25 14:50 Page 18

19
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 con-
trol 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.
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 5
Photo 3
Photo 4
Photo 7
Screw of the
electrical box
Drain hose
Screws of the
left side of the
heat exchanger
Screws of the vane motor
Screws of
the motor
bed
Photo 6
Indoor coil thermistor
connector
Fan motor connector
Vane motor
connector
Hooks of the
motor band
Screw of
the lead
cover
Hexagon socket set screw
OB385-1.qxp 05.1.25 14:50 Page 19

20
PARTS LIST
11
1
2
3
4
5
6
7
8
E02 763 234
E02 764 234
E02 959 000
E02 763 067
E02 959 010
E02 408 142
E02 763 100
E02 764 100
E02 763 975
E02 408 970
E02 751 970
BOX(WH)
BOX(WH)
PANEL ASSEMBLY(WH)
SCREW CAP(WH)
FRONT PANEL(WH)
CATCH
CATECHIN AIR FILTER
CATECHIN AIR FILTER
CORNER BOX (RIGHT)
INSTALLATION PLATE
INSTALLATION PLATE
Symbol
in Wiring
Diagram
Q'ty/unit
1
1
2
1
2
2
1
1
Including No.3,4,5
2PCS/SET
2PCS/SET
Remarks
Part No.
No.
Part Name MSC-GA20VB-
E1 (WH)
1
1
2
1
2
2
1
1
1
1
2
1
2
2
1
1
1
1
1
11 1
E02 749 426
E02 527 083
9
10 REMOTE CONTROLLER
REMOTE CONTROLLER HOLDER
MSC-GA25VB-
E1 (WH) MSC-GA35VB- E1 (WH)
KP1A
1 (W)
7
2
4
MSC-GA20VB - (WH)
MSC-GA25VB - (WH)
MSC-GA35VB - (WH)
E1
E1
E1
3
8 (W)
11-2. ACCESSORY AND REMOTE CONTROLLER
11-1. INDOOR UNIT STRUCTURAL PARTS
11-1. INDOOR UNIT STRUCTURAL PARTS
56 (W)
10
11-2. ACCESSORY AND
REMOTE CONTROLLER
9
Optional parts
(See page 22.)
(W) These figures show about MSC-GA35VB.
OB385-1.qxp 05.1.25 14:50 Page 20