Mitsubishi Electric MSH-A18ND-S1 User manual

CONTENTS
1. TECHNICAL CHANGES ····································2
2. PART NAMES AND FUNCTIONS······················2
3. SPECIFICATION·················································4
4. OUTLINES AND DIMENSIONS ·························5
5. WIRING DIAGRAM ············································6
6. REFRIGERANT SYSTEM DIAGRAM················7
7. SERVICE FUNCTIONS ······································8
8. TROUBLESHOOTING······································10
9. DISASSEMBLY INSTRUCTIONS ····················18
10. PARTS LIST······················································20
11. RoHS PARTS LIST···········································23
SPLIT-TYPE, HEAT PUMPAIR CONDITIONERS
Outdoor unit service manual
MUH-A·ND Series (OB428)
MSH-A18ND
MSH-A24ND
TM
Wireless type
Models
MSH-A18ND -
MSH-A24ND - S1
S1
SERVICE MANUAL
INDOOR UNIT No. OB427
REVISED EDITION-B
Please void OB427 REVISED EDITION-A.
Revision B:
•Remote controller model has been changed.
•RoHS PARTS LIST has been added.
NOTE:
This service manual describes technical data of the indoor units.
RoHS compliant products have <G> mark on the spec name plate.
For servicing of RoHS compliant products, refer to the RoHS PARTS LIST (RoHS compliant).
OB427B-1.qxp 07.5.16 3:30 PM Page 1
All manuals and user guides at all-guides.com
all-guides.com

TECHNICAL CHANGES
2
1
PART NAMES AND FUNCTIONS
2
INDOOR UNIT
Grille
Air inlet
Remote controller
Remote control
receiving section
Air cleaning filter
(White bellows type)
Horizontal vane
Vertical vanes
Catechin air filter
(When the grille is opened)
Operation section Display section
Emergency operation switch
Operation indicator lamp
Remote control
receiving section
Front panel
MSH-A18ND
MSH-A24ND
MSH-18TN - ➔MSH-A18ND -
MSH-24TN - ➔MSH-A24ND -
1. Model name has been changed.
2. Grille design has been changed.
3. Unit size has been changed.(W 1,015a o H 320a o D 190a➔W 1,100a o H 325a o D 258a)
4. Electricity receiving unit has been changed from indoor unit to outdoor unit.
S1S1
S1S1
ACCESSORIES
1
2
3
4
5
6
7
8
Installation plate
Installation plate fixing screw 4 o25 mm
Remote controller holder
Fixing screw for 3o3.5 o1.6 mm (Black)
Battery (AAA) for remote controller
Wireless remote controller
Air cleaning filter
Felt tape (Used for left or left-rear piping)
1
7
1
2
2
1
2
1
MSH-A18ND
MSH-A24ND
Revision A:
•Parts No. of 10.PARTS LIST has been revised.
Revision B:
•Remote controller model has been changed. (KP0A ➔KM04A)
Both remote controllers can be used as alternative.
•RoHS PARTS LIST has been added.
OB427B-1.qxp 07.5.17 7:35 AM Page 2
All manuals and user guides at all-guides.com

REMOTE CONTROLLER
MSH-A18ND
MSH-A24ND
3
ON/OFF
TOO
COOL
PM
AM
TOO
WARM
ON/OFF
FAN
TOO
WARM TOO COOL
VANE
MODE
ECONO COOL
STOP
START
HR.
MIN.
WIDE VANE
LONG
I FEEL COOL
HEAT
DRY
PM
CLOCK
AM
RESET CLOCK
Open the front lid.
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 button
(Horizontal vane button)
CLOCK SET button
LONG button
WIDE VANE button
(Vertical vane button)
Indication of remote controller
model is on back.
OB427B-1.qxp 07.5.16 3:30 PM Page 3
All manuals and user guides at all-guides.com

SPECIFICATION
4
3
Indoor model
Function
Power supply
Air flow
(High/Med./Low)
Running current
Power input
Power factor
Model
Current
Winding
resistance (at 20:)
Dimensions WOHOD
Weight
Air direction
Sound level (High/Med./Low)
Fan speed (High/Med./Low)
Fan speed regulator
Remote controller model
K/h
A
W
%
A
"
mm
kg
dB
rpm
Single phase
220V, 60Hz
768/642/516
0.28
60
97
RC4N32-AA
0.28
WHT-BLK 205.5
BLK-RED 217.6
1,100O325O258
16
5
42/37/32
1,070/920/780
3
KP0A, KM04A
Cooling Heating Cooling
954/822/684
1,280/1,130/970
Heating
954/834/726
1,280/1,150/1,020
Single phase
220V, 60Hz
0.37
81
99
RC4V40-AA
0.37
WHT-BLK 138.2
BLK-RED 159.0
1,100O325O258
16
5
47/42/37
3
KP0A, KM04A
Electrical
data
Fan
motor
Special
remarks
Capacity
MSH-A18ND MSH-A24ND
NOTE: Test conditions are based on ISO 5151.
Cooling : Indoor DB27°C WB19°C Heating : Indoor DB20°C WB 15.5°C
Outdoor DB35°C WB(24°C) Outdoor DB 7°C WB 6°C
Indoor-Outdoor piping length : 5m
Test conditions are based on SSA 356/366.
Cooling : Indoor DB29°C WB19°C Heating : Indoor DB21°C
Outdoor DB46°C WB24°C Outdoor DB 7°C WB 6°C
Indoor-Outdoor piping length : 7.5m
OB427B-1.qxp 07.5.16 3:30 PM Page 4
All manuals and user guides at all-guides.com

5
OUTLINES AND DIMENSIONS
4
258
162
19
58
47
7.5
315
255.547
2.5
98 173
98 173414.5 414.5
5
253
791
56
1068
1100
325
Air out
Air in
Insulation [28
Drain hose [16
(Connected part O.D)
Installation plate
Wall hole [75
Wireless remote controller
Installation plate Indoor unit
{
Liquid line [6.35-0.5m
Gas line [12-0.43m
Insulation [50 O.D
[32 I.D
{
Liquid line [9.52-0.5m
Gas line [12-0.43m
Insulation [50 O.D
[32 I.D
for MSH-A18ND
for MSH-A24ND
INDOOR UNIT
MSH-A18ND
MSH-A24ND Unit: mm
OB427B-1.qxp 07.5.16 3:30 PM Page 5
All manuals and user guides at all-guides.com

6
WIRING DIAGRAM
5
MSH-A18ND
INDOOR UNIT
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. : Connector
: Terminal block
NOTES:
SYMBOL
C11
F11
HIC1
MF
NAME
INDOOR FAN CAPACITOR
FUSE (3.15A)
DC/DC CONVERTER
FAN MOTOR (INNER PROTECTOR)
SYMBOL
MV1
MV2
NR11
RT11
NAME
VANE MOTOR (HORIZONTAL)
VANE MOTOR (VERTICAL)
VARISTOR
ROOM TEMPERATURE THERMISTOR
SYMBOL
RT12
SR141
TB
NAME
INDOOR COIL THERMISTOR
SOLID STATE RELAY
TERMINAL BLOCK
RT11
RT12
BLK
GRY
YLW
BRN
WHT
RED
MF
SR141
CN
121
CN
112
CN
111
C11
CN211
HIC1
151
CN
MV2 MV2 MV1
15
NR11
ELECTRONIC CONTROL P.C. BOARD
F11
220V~
BRN
CN201
12V
TO OUTDOOR
UNIT
CONNECTING
GRN/YLW
BLU
RED
CN
101
CN
102
DISPLAY
P.C.BOARD RECEIVER P.C.BOARD REMOTE
CONTROLLER
TAB12
TB
33
3
3
N
2
2
3
13
1
4
INDOOR UNIT
BLK
GRY
YLW
BRN
WHT
RED
MF
3
SR141
4
3
1
1
4
2
3
CN
121
C11
HIC1
MV1
RT13
CN112
151
CN
MV2
15
RT12
RT11
111
CN
CN211
NR11
ELECTRONIC CONTROL P.C. BOARD
F11
220V~
BRN
CN201
12V
TO OUTDOOR
UNIT
CONNECTING
MV2
BLU
RED
CN
101
CN
102
DISPLAY
P.C.BOARD RECEIVER P.C.BOARD REMOTE
CONTROLLER
33
TAB12
TB
3
N
2
1
2
3
GRN/YLW
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. : Connector
: Terminal block
NOTES:
SYMBOL
SR141
TB
SYMBOL
MV2
NR11
RT11
RT12
RT13
SYMBOL
C11
F11
HIC1
MF
MV1
INDOOR FAN CAPACITOR
FUSE (3.15A)
DC/DC CONVERTER
INDOOR FAN MOTOR (INNER PROTECTOR)
VANE MOTOR (HORIZONTAL)
VANE MOTOR (VERTICAL)
VARISTOR
ROOM TEMPERATURE THERMISTOR
INDOOR COIL THERMISTOR (MAIN)
INDOOR COIL THERMISTOR (SUB)
SOLID STATE RELAY
TERMINAL BLOCK
NAME NAME NAME
MSH-A24ND
OB427B-1.qxp 07.5.16 3:30 PM Page 6
All manuals and user guides at all-guides.com
all-guides.com

7
REFRIGERANT SYSTEM DIAGRAM
6
Refrigerant flow in cooling
Refrigerant flow in heating
Strainer
#50
MSH-A18ND
INDOOR UNIT
Indoor
heat
exchanger
Room temperature
thermistor
RT11
Refrigerant pipe [12.7
(with heat insulator)
Flared connection
Flared connection
Indoor coil
thermistor
RT12
Refrigerant pipe [6.35
(with heat insulator)
Distributor
Strainer
#50
MSH-A24ND
INDOOR UNIT
Indoor
heat
exchanger
Room temperature
thermistor
RT11
Refrigerant pipe [15.88
(with heat insulator)
Flared connection
Flared connection
Refrigerant pipe [6.35
(with heat insulator)
Distributor
Unit:mm
Indoor coil
thermistor
RT12(main)
Indoor coil
thermistor
RT13(sub)
OB427B-1.qxp 07.5.16 3:30 PM Page 7
All manuals and user guides at all-guides.com

8
SERVICE FUNCTIONS
7
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. “Auto restart function”automatically starts operation in the same
mode just before the shutoff of the main power. 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 tempera-
ture.
7-3. AUTO RESTART FUNCTION
7-1. TIMER SHORT MODE
For service, set time can be shortened by short circuit of JPG and JPS on the electronic control P.C. board.
The time will be shortened as follows.
Set time : 1 minute ➔ 1-second
Set time : 3 minute ➔ 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.)
MSH-A18ND
MSH-A24ND
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
7-2. 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 :
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.
NOTE : For modification, take out the batteries and press the OPERATE/STOP(ON/OFF) button 2 or 3 times at first.
After modification, put back the batteries then press the RESET button.
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 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.
Remote controller model : KP0A
Remote controller model : KM04A
J2
J1 J1
J2
OB427B-1.qxp 07.5.16 3:30 PM Page 8
All manuals and user guides at all-guides.com

9
How to release “AUTO RESTART FUNCTION”
1Turn off the main power for the unit.
2Pull out the electronic control P.C. board, the receiver P.C.
board and the display P.C.board. (Refer to 9-2.)
3Solder jumper wire to JR07 on the indoor
electronic control P.C. board. (Refer to 8-6.)
JR07
IC152
CN151
CN112
CN111
CN121
SW1
IC101
RA102
C11
CN201
CN211
TAB12
Operation
1If the main power has been cut, the operation settings remain.
2After 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 with the
remote controller.
•If main power is turned off or a power failure occurs 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 appliances 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 to the system that allows the units to start one by one.
OB427B-1.qxp 07.5.16 3:30 PM Page 9
All manuals and user guides at all-guides.com

10
TROUBLESHOOTING
8
8-1. 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 of the following during servicing
(1) Before servicing the air conditioner, be sure to first turn off the remote controller to stop the main 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) Before servicing, check that the connector and terminal are connected properly.
(3) When the electronic control P.C. board seems to be defective, check the copper foil pattern for disconnection and the
components for bursting and discolouration.
(4) When troubleshooting, refer to 8-2. and 8-3.
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.
1Remove the front lid and insert batteries.
Then reattach the front lid.
Lead wiring Housing point
MSH-A18ND
MSH-A24ND
RESET button
2Press the RESET button with tip end of ball point
pen or the like, and then use the remote controller.
NOTE : 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 is correct.
OB427B-1.qxp 07.5.16 3:30 PM Page 10
All manuals and user guides at all-guides.com

11
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 when
the EMERGENCY
OPERATION
switch is pressed.
Outdoor unit
doesn't
operate
when the
EMERGENCY
OPERATION
switch is pressed.
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 8-6.
"Test point
diagram and
voltage".
Refer to
"Check of
outdoor unit".
Refer to 8-5.B
"Check of
remote controller
and receiver
P.C. board".
Flash on and
off at 0.5
-
second
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
Refer to
8-5. D
"How to
check
mis-wiring
(When
outdoor unit
doesn't
work)".
Check room
temperature
thermistor
and indoor
coil thermis-
tor.
Refer to 8-6.
"Test point
diagram and
voltage".
Refer to
8-5. A
"Check of
indoor fan
motor".
Refer to
"Check of
outdoor
thermistor".
Replace the
deicer
P.C. board.
4-time flash
Cause:
Indoor unit
•Trouble of
indoor unit
control
system
Replace the
indoor
electronic
control
P.C. board.
Refer to outdoor unit service manual.
1. Check indoor /
outdoor
connecting wire.
2. Refer to 8-5.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.
Refer to
"Check of
outdoor unit".
Refer to
"Check of
R.V. coil".
8-2. Instruction of troubleshooting
OB427B-1.qxp 07.5.16 3:30 PM Page 11
All manuals and user guides at all-guides.com
all-guides.com

12
8-3. Troubleshooting check table
•The following indication applies regardless of shape of the indicator.
•Before taking measures, make sure that the symptom reappears for accurate troubleshooting.
When the indoor unit has started operation and the following detection method has detected an abnormality
(the first detection after the power ON), the indoor electronic control P.C. board turns OFF the indoor fan motor with the
OPERATION INDICATOR lamp flashing.
Operation Indicator Lighted
Not lighted
No.
1
2
4
6
SymptomOperation indicator lamp
Condition Correspondence
Mis-Wiring
Outdoor
thermistor
Outdoor
control
system
Indoor coil
thermistor
3 minutes after power supply turns ON, when
serial signal is not received.
<Thermistor short>
Thermistors are abnormal when they short
after compressor start-up.
<Thermistor open>
Thermistors are abnormal when they open
after compressor start-up.
However, discharge temperature thermistor is
abnormal when open circuit is detected more
than 10 minutes after compressor start-up.
When it cannot properly read data in the
nonvolatile memory of the deicer P.C. board,
outdoor unit stops.
•Shortage of refrigerant
•Check the deicer P.C.
board.
Refer to "Check of outdoor
thermistor".
Refer to outdoor unit service
manual.
•Check the deicer P.C. board.
Refer to outdoor unit service
manual.
•Refer to 8-5. D"How to check
mis-wiring ".
3Indoor fan
motor
Abnormal
point
Outdoor unit
does not
operate.
Room
temperature
thermistor
Detect Indoor coil/room temperature
thermistor short or open circuit every 8
seconds during operation.
•Refer to the characteristics of
main indoor coil thermistor,
sub indoor coil thermistor,
and room temperature
thermistor in 8-6.
Indoor fan repeats
12 seconds ON
and 3minutes OFF.
When the indoor
fan breaks, the fan
keeps stopping.
When rotational frequency feedback signal is
not emitting during 12-second indoor fan
operation.
•Refer to 8-5. A"Check of
indoor fan motor".
Indoor
control
system
When it cannot properly read data in the
nonvolatile memory of the indoor electronic
control P.C. board.
Outdoor unit
does not
operate.
Outdoor unit
does not
operate.
•Check the indoor electronic
control P.C. board.
Outdoor unit
does not
operate.
Outdoor unit
does not
operate.
5
0.5-second ON
0.5-second OFF
2-time flash
2.5-second OFF
3-time flash
2.5-second OFF
4-time flash
2.5-second OFF
6-time flash
2.5-second OFF
7-time flash
2.5-second OFF
·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.
OB427B-1.qxp 07.5.16 3:30 PM Page 12
All manuals and user guides at all-guides.com

13
MSH-A18ND
MSH-A24ND
Part name FigureCheck method and criterion
Indoor fan motor(MF)
MSH-A18ND
INNER FUSE
145:CUT OFF
MSH-A24ND
INNER
PROTECTOR
135i5:OPEN
Color of
lead wire
WHT –BLK
BLK –RED
MSH-A18ND
198 "~ 214 "
209 "~ 227 "
Measure the resistance with a tester.
(Part temperature 10˚C ~ 30˚C)
Normal
8 k"~ 20 k"
Room temperature
thermistor (RT11)
Indoor coil thermistor
(RT12(main), RT13(sub))
Horizontal vane
motor(MV1)
Vertical vane
motor(MV2)
Motor part
Sensor part
Measure the resistance between the terminals with a tester.
(Part temperature 10˚C ~ 30˚C)
Color of lead wire
BRN –YLW
YLW –GRY
Normal
4.5 ~ 5.5V
Measure the voltage power ON.
(When fan revolved one time)
0V➔5V➔0V
(Approx.)
Normal
282"~ 306 "
Measure the resistance between the terminal with a tester.
(Part temperature 10°C ~ 30°C)
BLK
RED
WHT
GRY
YLW BRN
MAIN
AUX
FUSE
BLK
RED
WHT
GRY
YLW BRN
MSH-A24ND
132 "~ 144 "
152 "~ 166 "
Normal
MSH-A18ND
MSH-A24ND
YLW
GRNORN
BRN
RED ROTOR
MAIN
AUX.
P
:INNER PROTECTOR
P
8-4. Trouble criterion of main parts
OB427B-1.qxp 07.5.16 3:30 PM Page 13
All manuals and user guides at all-guides.com

14
Yes
Yes
Check of indoor fan motor
A
Check of remote controller and receiver P.C. board
B
When OPERATION INDICATOR lamp flashes 3-time.
Indoor fan motor doesn’t operate.
Repair or replace the indoor fan motor.
Disconnect lead wires from connector CN211 on the indoor electronic control P.C. board.
Measure resistance between lead wires No.3 and No.4 and then No.1 and No.4.
Are lead wires connected?
Reconnect the lead wires.
Is soldered point of the connector
correctly soldered? Resolder it.
Is resistance 0 (short circuit) or ∞(open circuit)?
Indoor unit operates by pressing the EMERGENCY OPERATION switch, but doesn’t operate with the remote controller.
Replace the batteries.(Refer to 8-1.4.)
Turn on a radio to AM and press
OPERATE/STOP(ON/OFF) button 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?
Measure the voltage between receiver P.C. board connector CN301 No.1(+) and No.3(-) when the remote
controller button is pressed.
Is the voltage approx. 4V DC? Replace the indoor electronic control P.C.
board.
Replace the receiver P.C. board.
Replace the remote controller.
● Reinstall the unit away from lights.
● Attach a filter on receiving part.
Yes ( 0 or ∞)No
(others)
Yes
No
Yes
No
Press OPERATE/STOP(ON/OFF)
button on the remote controller.
Is LCD display on the the remote
controller visible?
Remove the 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
No(5V or 0V DC)
No
Turn OFF the power supply.
Check connector CN211 visually.
w Check if the remote controller is exclusive for this air conditioner.
Turn ON the power supply. Stop it if the unit operate.
Insert screwdriver into air outlet to rotate indoor fan
motor slowly for 1 revolution or over, and measure
voltage between No.2(+) and No.3(-) on CN121.
Replace the indoor electronic control P.C. board.
Does voltage repeat 0V DC and 5V DC?
Yes
No
8-5. Troubleshooting flow
OB427B-1.qxp 07.5.16 3:30 PM Page 14
All manuals and user guides at all-guides.com

15
Check of indoor electronic control P.C. board
C
Check the both “parts side”and “pattern
side”of indoor electronic control P.C.
board visually.
Replace the fuse.
Is fuse(F11) blown?
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.
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
Turn OFF the
power supply. Turn OFF the
power supply.
Varistor (NR11)
Indoor electronic
control P.C. board
Fuse (F11)
No No
The unit doesn’t operate with the remote controller. Also, the OPERATION INDICATOR lamp doesn’t light up by press-
ing the EMERGENCY OPERATION switch.
OB427B-1.qxp 07.5.16 3:30 PM Page 15
All manuals and user guides at all-guides.com

16
How to check mis-wiring
D
1. Turn OFF the power supply (outdoor unit) and disconnect indoor and outdoor connecting
wire 3on indoor side.
2. Short-circuit terminal block N-3by lead wire.
3. Turn ON the power supply (outdoor unit) and press EMERGENCY OPERATION switch once.
During EMERGENCY OPERATION, is there
10V DC between both ends of R601 on the
deicer P.C. board?
(By tester, the stylus is between 5 ~10V.)
Refer to outdoor unit service manual.
Start
No
No
Is there 20V DC between both ends of
PS132 on the indoor electronic control P.C.
board ?
( By tester, the stylus is between 0 ~ 20V. )
•Turn ON the power supply. (outdoor unit)
•Press EMERGENCY OPERATION switch once.
Is this mis-wiring, poor contact,
or wire disconnection?
Correct them.
Replace the indoor electronic
control P.C. board.
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
Is there 5V DC between J205 + -J101 -
/ J101 + -J401 - on the deicer P.C. board?
Yes
Yes
After 3 minutes, mis-wiring is indicated
(0.5-second ON, 0.5-second OFF)
on OPERATION INDICATOR
lamp on indoor unit.w
wShort circuit of JPG and JPS on the indoor electronic control
P.C. board enables self -check to be displayed in 3 seconds.
•Turn OFF the power supply.
(outdoor unit)
•Connect ON indoor/ outdoor connecting
wire.
Turn ON the power supply. (outdoor unit)
When OPERATION INDICATOR lamp flashes ON and OFF in every 0.5-second.
Outdoor unit doesn’t operate.
OB427B-1.qxp 07.5.16 3:30 PM Page 16
All manuals and user guides at all-guides.com
all-guides.com

17
8-6. Test point diagram and voltage
MSH-A18ND MSH-A24ND
Indoor electronic control P.C. board
Indoor coil thermistor(RT12(main), RT13(sub))
Room temperature thermistor (RT11)
Resistance(k")
Fan motor power supply
Fuse (F11)
250V AC 3.15A
}Power supply input
220V AC
+}5V DC
Indoor coil
thermistor(RT12(main))
Timer short mode point
(JPS, JPG)
(Refer to 7-1.)
Emergency operation
switch
+
}
12V DC
Room temperature ther-
mistor(RT11)
Release of “Auto restart function”
Solder jumper wire to JR07.
(Refer to 7-3.)
MSH-A24ND
Indoor coil
thermistor(RT13(sub))
PS132
Receiver P.C. board
OB427B-1.qxp 07.5.16 3:30 PM Page 17
All manuals and user guides at all-guides.com

18
DISASSEMBLY INSTRUCTIONS
9
MSH-A18ND MSH-A24ND
INDOOR UNIT
(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.
Photo 1
Photo 2
Front panel
Screws
2. Removing the electronic control P.C. board, the receiver
P.C. board and the display P.C. board
(1) Remove the front panel. (Refer to 1.)
(2) Remove the screw of the electrical cover.
Remove the electrical cover.
(3) Remove the screws of the V.A. clamp.
Remove the V.A. clamp.
(4) Remove the screw of the terminal block.
(5) Remove the screws of the ground wire.
(6) Disconnect all the connectors and all the lead wires on the
electronic control P.C. board.
(7) Remove the R.L holder.
(8) Remove the electronic control P.C. board.
(9) Open the R.L holder, remove the receiver P.C. board and
the display P.C. board.
Indoor
electronic
control
P.C.board
Vane motor
connector
Fan motor
connectors
Screws of the ground wire
Screw of
the electrical
cover
Screw of the
V.A. clamp
R.L
holder
Screw of
the terminal
block
Receiver
P.C.
board
OB427B-1.qxp 07.5.16 3:30 PM Page 18
All manuals and user guides at all-guides.com

19
OPERATING PROCEDURE PHOTOS
Photo 4
Photo 6
Vane motors
Indoor
coil
thermistor
3. Removing the electrical box
(1) Remove the front panel. (Refer to 1.)
(2) Remove the electrical cover. (Refer to 2.)
(3) Disconnect the connector of the indoor coil thermistor.
(4) Disconnect the motor connector (CN211 and CN121) and
the vane motor connector (CN151) on the electronic
control P.C. board.
(5) Remove the screws of ground wire.
(6) Remove the fan motor lead wire and indoor coil thermistor
from the electrical box.
(7) Remove the lead wire of vane motor from the bottom of
electrical box.
(8) Remove the screw fixing the electrical box and remove the
electrical box.
4. Removing the vane motor
(1) Remove the front panel. (Refer to 1.)
(2) Remove the electrical cover. (Refer to 2.)
(3) Remove the lead wire of vane motor. (Refer to 3.)
(4) Remove the R.L. holder.
(5) Pull out the drain hose from the nozzle assembly and
remove the nozzle assembly.
(6) Remove the screws of the vane motor and disconnect the
connector.
(7) Remove the vane motor.
Screws fixing the fan motor
5. Removing the line flow fan and the indoor fan 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 and
remove the nozzle assembly.
(4) Remove the water cut.
(5) Slide the hole cover and remove the hole cover.
(6) Remove the hexagon socket set screw from the line flow
fan.
(7) Remove the screws fixing the fan motor and remove the
fan motor. (Be careful not to drop the fan motor because it
is heavy.)
(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.
Screws fixing
the left side
of the heat
exchanger
Screws
of the
vane
motor
Screws of the
vane motor
Vane motor
Photo 5
Photo 7
Photo 8
Hole
cover
Water cut
Photo 3
Screw of the
electrical cover
Screws of the ground wire
Screw of the
electrical box
OB427B-1.qxp 07.5.16 3:30 PM Page 19
All manuals and user guides at all-guides.com

20
PARTS LIST (non-RoHS compliant)
10
MSH-A18ND
MSH-A24ND
10-1. INDOOR UNIT STRUCTURAL PARTS
MSH-A24ND - S1 MSH-A18ND - S1
E02 527 970
E02 685 234
E02 888 000
E02 408 142
E02 685 067
E02 888 010
E02 534 100
E02 685 975
E02 888 007
INSTALLATION PLATE
BOX
FRONT PANEL ASSEMBLY
CATCH
SCREW CAP
GRILLE
CATECHIN AIR FILTER
AIR CLEANING FILTER
CORNER BOX RIGHT
LAMP PANEL
Symbol
in Wiring
Diagram
Q'ty/unit
Including No.4,5,6
4PCS/ SET
3PCS/ SET
MAC-1700FT
RemarksPart No.
NO. Part Name
1
2
3
4
5
6
7
8
9
10
1
1
1
4
3
1
2
2
1
1
1
1
1
4
3
1
2
2
1
1
10-2. INDOOR UNIT HEAT EXCHANGER
2
4
5
7
6
1
9
8 (See 10-5.)
11
12
3
E02 891 620
E02 893 620
E02 179 667
E02 527 666
E02 151 667
INDOOR HEAT EXCHANGER
INDOOR HEAT EXCHANGER
UNION (GAS)
UNION (GAS)
UNION (LIQUID)
{12.7
{15.88
{6.35
11
12
13
1
1
1
1
1
1
10-2. INDOOR UNIT HEAT EXCHANGER
10-1. INDOOR UNIT STRUCTURAL PARTS
Part number that is circled is not shown in the illustration.
13
OB427B-1.qxp 07.5.16 3:30 PM Page 20
All manuals and user guides at all-guides.com