Mitsubishi Electric MSZ-A18YV User manual

SERVICE MANUAL
CONTENTS
1. PART NAMES AND FUNCTIONS······················2
2. SPECIFICATION·················································4
3. NOISE CRITERIA CURVES ·······························5
4. OUTLINES AND DIMENSIONS ·························6
5. WIRING DIAGRAM ············································7
6. REFRIGERANT SYSTEM DIAGRAM ················8
7. SERVICE FUNCTIONS ······································9
8. TROUBLESHOOTING······································11
9. DISASSEMBLY INSTRUCTIONS ····················20
10. PARTS LIST······················································22
11. OPTIONAL PARTS·······················BACK COVER
Models
MSZ-A18YV -
MSZ-A24YV -
MSZ-A26YV - E1
E1
E1
SPLIT-TYPE AIR CONDITIONERS
MSZ-A18YV -
MSZ-A24YV -
MSZ-A26YV - E1
E1
E1
NOTE:
This service manual describes technical data of the indoor unit.
•Refer to the service manual OB346 when MSZ-A18YV - , MSZ-A24YV - or MSZ-A26YV -
is connected with MUZ-A18YV - , MUZ-A24YV - or MUZ-A26YV - .
•Refer to the service manual OB319 when MSZ-A18YV - , MSZ-A24YV - or MSZ-A26YV -
is connected with MXZ-A26WV - or MXZ-A32WV - as multi system units.
E1E1
E1E1E1
E1E1E1
E1E1E1
No. OB345
REVISED EDITION-A
Revision A :
• Parts numbers of indoor fan motor and motor band have
been changed.
•
Another type of the electronic control P.C.board (TYPE 2)
has been added to the original one (TYPE 1).
They are both compatible with MSZ-A18/24/26YV-
.
• Some descriptions have been modified.
E
Please void OB345.
INDOOR UNIT

2
PART NAMES AND FUNCTIONS
1
INDOOR UNIT
Grille
(When the grille is opened)
Remote controller
Operation section Display section
Emergency operation switch
Operation indicator lamp
Air inlet
To Breaker
Power supply cord
Remote control
receiving section
Air cleaning filter (option)
(White bellows type)
Horizontal vane
Vertical vanes
Catechin air filter
Remote control
receiving section
MSZ-A18YV -
MSZ-A24YV -
MSZ-A26YV - E1
E1
E1
ACCESSORIES
Indoor unit
1
2
3
4
5
6
7
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
Felt tape (Used for left or left-rear piping)
1
7
1
2
2
1
1
MSZ-A18YV -
MSZ-A24YV -
MSZ-A26YV -
E1
E1
E1
Use the specified refrigerant only
Never use any refrigerant other than that specified.
Doing so may cause a burst, an explosion, or fire when the unit is being used, serviced, or disposed of.
Correct refrigerant is specified in the manuals and on the spec labels provided with our products.
We will not be held responsible for mechanical failure, system malfunction, unit breakdown or accidents caused by
failure to follow the instructions.
Revision A :
• Parts numbers of indoor fan motor and motor band have been changed.
• Another type of the electronic control P.C.board (TYPE 2) has been added to the original one (TYPE 1).
They are both compatible with MSZ-A18/24/26YV- .
• Some descriptions have been modified.
E
OB345A

REMOTE CONTROLLER
MSZ-A18YV -
MSZ-A24YV -
MSZ-A26YV - E1
E1
E1
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.
3
OB345A

SPECIFICATION
4
2
Indoor model
Function
Power supply
Air flow
(High/Med. /Low )
Power outlet
Running current
1
Power input 1
Auxiliary heater
Power factor
1
Fan motor current 1
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:)
Thermistor RT13(at 25:)
Remote controller model
K/h
A
A
W
A(kW)
%
A
"
mm
kg
dB
rpm
k"
k"
k"
MSZ-A18YV - E1
Single phase
230V, 50Hz
852/690 /498
10
0.30
60
—
87
0.30
RC4V32-AA
WHT-BLK 293
BLK-RED 146
1,100O325O258
16
5
43/38 /31
1,120/940 /720
3
10
10
10
KP0A
Cooling Heating
MSZ-A24YV - E1
Single phase
230V, 50Hz
10
0.34
69
—
87
0.34
RC4V40-AA
WHT-BLK 138.2
BLK-RED 159.0
1,100O325O258
16
5
48/40 /32
3
10
10
10
KP0A
Cooling
1,032/768 /522
1,310/1030 /750
Heating
1,032/786 /522
1,310/1050 /750
Electrical data
Fan motor
Special remarks
Capacity
w w
w w
ww
ww
ww
ww
w w
ww
ww
w w
ww
NOTE: Test conditions are based on ISO 5151.
Cooling : Indoor Dry-bulb temperature 27°C Wet-bulb temperature 19°C
Outdoor Dry-bulb temperature 35°C Wet-bulb temperature(24°C)
Heating : Indoor Dry-bulb temperature 20°C Wet-bulb temperature 15.5°C
Outdoor Dry-bulb temperature 7°C Wet-bulb temperature 6°C
Indoor-Outdoor piping length 5m
wReference value
1 Measured under rated operating frequency.
Indoor model
Function
Power supply
Air flow
(High/Med. /Low )
Power outlet
Running current
1
Power input 1
Auxiliary heater
Power factor
1
Fan motor current 1
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:)
Thermistor RT13(at 25:)
Remote controller model
K/h
A
A
W
A(kW)
%
A
"
mm
kg
dB
rpm
k"
k"
k"
MSZ-A26YV - E1
Single phase
230V, 50Hz
10
0.34
69
—
88
0.34
RC4V40-AA
WHT-BLK 138.2
BLK-RED 159.0
1,100O325O258
16
5
48/40 /33
3
10
10
10
KP0A
Cooling
1,032/798 /564
1,310/1,060 /800
Heating
1,032/816 /564
1,310/1,080 /800
Electrical data
Fan motor
Special remarks
Capacity
w w
ww
ww
w w
ww w
ww
ww
w
•Refer to the service manual OB346 when MSZ-A18YV - , MSZ-A24YV - or MSZ-A26YV - is connected with
MUZ-A18YV - , MUZ-A24YV - or MUZ-A26YV - .
•Refer to the service manual OB319 when MSZ-A18YV - , MSZ-A24YV - or MSZ-A26YV - is connected with
MXZ-A26WV - or MXZ-A32WV - as multi system units.
E1E1
E1E1E1
E1E1E1
E1E1E1
OB345A

5
NOISE CRITERIA CURVES
3
90
80
70
60
50
40
30
20
10 63 125 250 500 1000 2000 4000 8000
NC-60
NC-50
NC-40
NC-30
NC-20
NC-70
BAND CENTER FREQUENCIES, Hz
Test conditions,
Cooling : Dry-bulb temperature 27: Wet-bulb temperature 19:
APPROXIMATE
THRESHOLD OF
HEARING FOR
CONTINUOUS
NOISE
43
SPL(dB(A)) LINE
High
FAN SPEED
Heating : Dry-bulb temperature 20: Wet-bulb temperature 15.5:
OCTAVE BAND SOUND PRESSURE LEVEL, dB re 0.0002 MICRO BAR
MSZ-A18YV - E1 MSZ-A24YV -
MSZ-A26YV - E1
E1
2.5+ 440V
250V 3.15A
MP20/MP20
TNR10V511K410
S201DH1N
3P
INDOOR UNIT
Item Model
Indoor fan capacitor
Fuse
Vane motor
Varistor
Solid state relay
Terminal block
Indoor fan motor thermal fuse
(C11)
(F11)
(MV1/ MV2)
(NR11)
(SR141)
(TB)
MSZ-A24YV -E1
MSZ-A18YV -E1 MSZ-A26YV -E1
145:
Specifications and rating conditions of main electric parts
90
80
70
60
50
40
30
20
10 63 125 250 500 1000 2000 4000 8000
OCTAVE BAND SOUND PRESSURE LEVEL, dB re 0.0002 MICRO BAR
BAND CENTER FREQUENCIES, Hz
APPROXIMATE
THRESHOLD OF
HEARING FOR
CONTINUOUS
NOISE
NC-60
NC-50
NC-40
NC-30
NC-20
NC-70
Test conditions,
Cooling : Dry-bulb temperature 27: Wet-bulb temperature 19:
48
SPL(dB(A)) LINE
High
FAN SPEED
Heating : Dry-bulb temperature 20: Wet-bulb temperature 15.5:
INDOORUNIT
WALL
MICROPHONE
0.8m
1m
OB345A

6
OUTLINES AND DIMENSIONS
4
258
159
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 MSZ-A18/A24YV
for MSZ-A26YV
Power supply cord
Lead to right 2.0m
Lead to left 1.0m
INDOOR UNIT
MSZ-A18YV -
MSZ-A24YV -
MSZ-A26YV - E1
E1
E1 Unit: mm
OB345A

7
WIRING DIAGRAM
5
MSZ-A18YV - E1 MODEL WIRING DIAGRAM
INDOOR UNIT
CN112
1RT12
2
3
4RT13
12V
TO OUTDOOR
UNIT
CONNECTING
BRN
BLU
GRN/YLW
BLK
GRY
YLW
BRN
WHT
RED
3
SR141
4
3
1
CN
121
C11
HIC1
TRANS
MV1
151
CN
MV2
15
RT11
111
CN
CN211
NR11
ELECTRONIC CONTROL P.C. BOARD
F11
3
N
LBRN
1
2
3
CN201
MV2
BLU
RED
CN
101
CN
102
DISPLAY
P.C. BOARD
RECEIVER
P.C. BOARD
REMOTE
CONTROLLER
33
TAB12
TB
6
5
4
3
2
MF
1
POWER
SUPPLY
CORD
~/N 230V
50Hz
CIRCUIT
BREAKER
PE
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
INDOOR FAN MOTOR (INNER FUSE)
SYMBOL
MV1
MV2
NR11
RT11
NAME
VANE MOTOR (HORIZONTAL)
VANE MOTOR (VERTICAL)
VARISTOR
ROOM TEMPERATURE THERMISTOR
SYMBOL
RT12
RT13
SR141
TB
NAME
INDOOR COIL THERMISTOR (MAIN)
INDOOR COIL THERMISTOR (SUB)
SOLID STATE RELAY
TERMINAL BLOCK
INDOOR UNIT
TB
TAB12
3 3
REMOTE
CONTROLLER
RECEIVER
P.C. BOARD
DISPLAY
P.C. BOARD
102
CN 101
CN
RED
BLU
MV2
CN201
3
2
1
BRN
L
N
3
F11
ELECTRONIC CONTROL P.C. BOARD
NR11
CN211
CN
111 RT11
RT12
15
MV2
CN
151
CN112
1
2
3
4RT13
MV1
TRANS
HIC1
C11
121
CN
1
3
4
SR141
3
RED
WHT
BRN
YLW
GRY
BLK
GRN/YLW
TO OUTDOOR
UNIT
CONNECTING
12V MF
CIRCUIT
BREAKER
POWER
SUPPLY
CORD
~/N 230V
50Hz
BLU
BRN
PE
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
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:
MSZ-A24YV -
MSZ-A26YV - E1
E1 MODELS WIRING DIAGRAM
OB345A

REFRIGERANT SYSTEM DIAGRAM
8
6
MSZ-A26YV - E1
INDOOR UNIT
Indoor
heat
exchanger
Flared connection
Room temperature
thermistor
RT11
Indoor coil
thermistor
RT13(sub)
Flared connection
Refrigerant pipe [15.88
(with heat insulator)
Refrigerant pipe [9.52
(with heat insulator)
Indoor coil
thermistor
RT12(main)
Strainer
#50
Refrigerant flow in cooling
Refrigerant flow in heating
MSZ-A18YV - E1
INDOOR UNIT
Indoor
heat
exchanger
Room temperature
thermistor
RT11
Refrigerant pipe [12.7
(with heat insulator)
Flared connection
Flared connection
Indoor coil
thermistor
RT12(main)
Refrigerant pipe[6.35
(with heat insulator)
Distributor
MSZ-A24YV - E1
INDOOR UNIT
Indoor
heat
exchanger
Room temperature
thermistor
RT11
Refrigerant pipe [15.88
(with heat insulator)
Flared connection
Flared connection
Indoor coil
thermistor
RT12(main)
Refrigerant pipe [6.35
(with heat insulator)
Distributor
Unit:mm
Indoor coil
thermistor
RT13(sub)
Indoor coil
thermistor
RT13(sub)
OB345A

9
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
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 :
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.)
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 bat-
teries and press the
OPERATE/STOP (ON/OFF) but-
ton 2 or 3 times at first.
After finish modification, put back
the batteries then press the
RESET button.
MSZ-A18YV -
MSZ-A24YV -
MSZ-A26YV - E1
E1
E1
Remote controller model : KP0A 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 accept 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.
OB345A

10
How to disable “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 page 20.)
3Solder jumper wire to the RESISTOR JR07 on the indoor electronic control P.C. board. (Refer to page 18. and 19)
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 indoor unit 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.
OB345A

11
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 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) 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 OPERATION INDICATOR lamp is flashing on and off before starting service
work.
(2) Before servicing check that the connector and terminal are connected properly.
(3) 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 discolouration.
(4) When troubleshooting, refer to the flow chart on page 12 and the check table on page 13.
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.
MSZ-A18YV - MSZ-A24YV -
MSZ-A26YV - E1
E1E1
RESET button
Insert the negative pole
of the batteries first.
Check if the polarity of
the battereis is correct.
2Press the RESET button with a thin instrument, and
then use the remote controller.
INFORMATION FOR MULTI SYSTEM AIR CONDITIONER
OUTDOOR UNIT : MXZ series
Multi system air conditioner can connect two or more indoor units with one outdoor unit.
•Unit won’t operate in case the total capacity of indoor units exceeds the capacity of outdoor units. Do not
connect indoor units beyond the outdoor unit capacity.
•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 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.
Lighted
Blinking
Operation Indicator
Lead wiring Housing point
<Incorrect> <Correct>
NOTE : 1. If the RESET button is not pressed, the remote controller may not operate correctly.
2. Do not use the leaking batteries.
OB345A

12
As for outdoor unit MUZ type, refer to service manual OB346.
As for outdoor unit MXZ type, refer to service manual OB319.
Start
Indoor unit
operates.
Outdoor unit
does not
operate.
Indoor unit
does not receive
the signal from
remote controller.
OPERATION INDICATOR
lamp on the indoor unit is
flashing on and off.
Outdoor unit
operates in
only Test Run
operation.
Outdoor unit
does not
operate
even in
Test Run
operation.
Indoor unit
operates, when
the EMERGENCY
OPERATION
switch is pressed.
Indoor unit
does not operate,
when the
EMERGENCY
OPERATION
switch is pressed.
Check room
temperature
thermistor.
Refer to
"Test point
diagram and
voltage" on
page 18 and 19.
Refer to
"Check of
inverter/
compressor".
Refer to
"Check of
remote controller
and receiver
P.C. board".
1. Check indoor/ outdoor
connecting wire.
(Check if the power
is supplied to the
indoor unit.)
2. Refer to
"Check of indoor
electronic control
P.C. board".
Unit does not
operate
normal
operation in
COOL or
HEAT mode.
Refer to
"Check of
R.V. coil".
Flash on and
off at 0.5-
second
interval
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
5-time flash
Cause:
Outdoor unit
• Outdoor
power
system
abnormality
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 D
"How to
check mis-
wiring and
serial signal
error (When
outdoor unit
does not
work)" on
page 17.
Check room
temperature
thermistor
and indoor
coil thermis-
tor.
Refer to
"Test point
diagram and
voltage" on
page 18 and
19.
Refer to A
"Check of
indoor fan
motor" on
page 15.
Refer to
"Check of
inverter/
compressor".
Refer to
"Check of
outdoor
thermistors".
Replace the
outdoor
electronic
control P.C.
board.
4-time flash
Cause:
Indoor unit
• Trouble of
indoor unit
control
system
Replace the
indoor
electronic
control
P.C. board.
Indoor unit operates.
Outdoor unit does not
operate normally.
8-2. Instruction of troubleshooting
OB345A

13
1. Troubleshooting check table
• The following indication applies regardless of shape of the indicator.
Operation Indicator Lighted
Not lighted
Before taking measures, make sure that the symptom reappears, for accurate troubleshooting.
Self check table
NOTE : When the indoor unit has started operation and the above 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.
No.
1
2
4
SymptomOperation indicator lamp Detection method
Checkpoint
0.5-second ON
0.5-second OFF
Mis-Wiring
or Serial
signal
Indoor coil
thermistor
3 minutes after power supply turns ON, when
serial signal is not received.
• Refer to D"How to check
mis-wiring and serial signal
error" on page 17.
3Indoor fan
motor
Abnormal
point
Outdoor unit
does not
operate.
Room
temperature
thermistor
2-time flash
2.5-second OFF
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 on page 18 and 19.
3-time flash
2.5-second OFF
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 emit during 12-second indoor fan
operation.
• Refer to A"Check of
indoor fan motor" on page 15.
4-time flash
2.5-second OFF
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.
5
6
Outdoor
power
system
Outdoor
thermistors
Outdoor
control
system
When compressor has stopped due to over
current protection or start-up failure protection
3 times in a row within 5 seconds after start-
up.
<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 outdoor electronic
control P.C. board.
• Shortage of refrigerant
• Replace the outdoor control
P.C. board.
Refer to "Check of outdoor
thermistor".
Refer to service manual
OB346 or OB319.
• Refer to "Check of inverter/
compressor".
Refer to service manual
OB346 or OB319.
• Replace the outdoor
electronic control P.C. board.
Refer to service manual
OB346 or OB319.
7
5-time flash
2.5-second OFF
6-time flash
2.5-second OFF
Outdoor unit
does not
operate.
Outdoor unit
does not
operate.
Outdoor unit
does not
operate.
Operation Indicator
MXZ type
Operation
mode
setting
Lighted
Blinking
Outdoor unit
operates but
indoor unit
does not
operate.
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.
• Unify the operation mode.
Refer to service manual
OB319.
7-time flash
2.5-second OFF
Right lamp flashes.
2.5-second OFF
8
· Flashing of the OPERATION INDICATOR lamp (the left-hand side lamp) indicates
possible abnormalities.
· The OPERATION INDICATOR lamp (the left-hand side lamp) is lighting during
normal operation.
OB345A

14
MSZ-A18YV -
MSZ-A24YV -
MSZ-A26YV - E1
E1
E1
Part name Figure
Check method and criterion
Indoor fan motor(MF)
MSZ-A18YV
INNER FUSE
145:CUT OFF
MSZ-A24/A26YV
INNER
PROTECTOR
135i5:OPEN
86i 15:CLOSE
Color of
lead wire
WHT – BLK
BLK – RED
Abnormal
Open or
short-circuit
MSZ-A18YV
282 "~ 305 "
141 "~ 152 "
Measure the resistance with a tester.
(Part temperature 10˚C ~ 30˚C)
Normal
8 k"~ 20 k"
Abnormal
Open or short-circuit
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
Abnormal
Remain 0V or 5V
Normal
4.5 ~ 5.5V
Measure the voltage power ON.
(When fan revolved one time)
0V➔5V➔0V
(Approx.)
Normal
282 "~ 306 "
Abnormal
Open or short-circuit
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
MSZ-A24/A26YV
132 "~ 144 "
152 "~ 166 "
Normal
MSZ-A18YV
MSZ-A24/A26YV
YLW
GRNORN
BRN
RED ROTOR
MAIN
AUX.
P
:INNER PROTECTOR
P
2. Trouble criterion of main parts
OB345A

15
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 does not 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 does not operate with the remote con-
troller.
Replace the batteries.(Refer to page 11.)
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?
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 approximately 4 VDC? 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
Switch 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 0 VDC)
No
Turn OFF the power supply.
Check connector CN211 visually.
wCheck 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 0 VDC and 5 VDC?
Yes
No
wPay enough attention to the
high voltage on the fan
motor connector.
OB345A

16
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.
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
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)
The unit does not operate with the remote controller. Also, the OPERATION INDICATOR lamp does not light up by
pressing the EMERGENCY OPERATION switch.
OB345A

17
When OPERATION INDICATOR lamp flashes ON and OFF in every 0.5-second.
Outdoor unit does not operate.
As for outdoor unit MUZ type, refer to service manual OB346.
As for outdoor unit MXZ type, refer to service manual OB319.
Reconnect the
power supply
cable.
Is there 325V DC between CN801 1and 3on the
outdoor electronic control P.C. board?
Replace the outdoor
electronic control P.C.
board.
Does the right side of OPERATION INDICATOR
lamp blink quickly?
w2 Mis-wiring may damage indoor electronic
control P.C. board during the operation.
Be sure to confirm the wiring is correct
before the operation starts.
Replace the indoor
electronic control
P.C. board.
No
Release the failure mode. w3
Yes
Yes
A
B
Turn OFF the power supply (Indoor/ outdoor unit).
Disconnect the indoor/ outdoor connecting wire.
Short-circuit indoor terminal block Nand 3.
Turn ON the power supply (Indoor/ outdoor unit).
During pressing the OPERATION SELECT button on the
remote controller, press the RESET button.
At first, release the RESET button.
And release the OPERATION SELECT button since all
LCD in operation display section of the remote controller
is displayed after 3 seconds.
Transmit the signal of remote controller, pressing
OPERATE/STOP (ON/OFF) button on the remote
controller.
(The above procedure allows OPERATION INDICATOR
lamp to indicate the failure-mode.)
Remove the short-circuit between indoor terminal block N
and 3.
Reconnect the indoor/ outdoor connecting wire.
Turn ON the power supply (Indoor/ outdoor unit).
Press the EMERGENCY OPERATION switch.
Is there amplitude of 5 to 10V DC between outdoor
terminal block Nand 3after 3 minutes (for confirmation of
serial signal)?
Yes
(light up or OFF)
After 3 minutes,
is mis-wiring
indicated on
OPERATION
INDICATOR lamp
on the indoor
unit?
Yes
No
· Turn OFF inverter-controlled lighting
equipment.
· Turn OFF the power supply and then
turn ON again (Indoor/ outdoor unit).
· Press the EMERGENCY
OPERATION switch.
B
· Reinstall
either the
unit or the
light each
other away.
· Attach a filter
on receiving
section of
the indoor
unit.
w3 Be sure to release the failure-mode
recall function after checking.
Procedure of release of failure-mode.
1Press the EMERGENCY
OPERATION switch.
2Turn OFF the power supply
(Indoor/ outdoor unit).
3Press the RESET button on the
remote controller.
Start
No
• Turn ON the power supply (Indoor/ outdoor unit).
•
Press once EMERGENCY OPERATION switch.
Is there any mis-wiring, poor contact,
or wire disconnection? w2
Correct them.
Yes
After 3 minutes, mis-wiring is indicated
(0.5-second ON, 0.5-second OFF)
on OPERATION INDICATOR
lamp on the 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.
Yes
Is there 230V AC between outdoor terminal
block Land N?
No Replace the
indoor/ outdoor
connecting wire.
A
No
Check of power
supply.
No
•The following indication
applies regardless of shape
of the indicator.
Blinking
Operation Indicator
AMP M
CLO CK
˚C
AMP M
How to check mis-wiring and serial signal error (when outdoor unit does not work)
D
OB345A

18
TEST POINT DIAGRAM AND VOLTAGE
MSZ-A18YV - MSZ-A24YV - MSZ-A26YV -
Indoor electronic control P.C. board
E1
E1E1
Fan motor power supply
(CN211)
Fuse (F11)
250 VAC 3.15A
}Power supply input
230 VAC
+}5 VDC
Timer short mode point
(JPS, JPG)
(Refer to 7-1.)
Emergency operation
switch
+
}
12 VDC
Indoor coil thermistor(RT12(main), RT13(sub))
Room temperature thermistor (RT11)
Resistance(k")
Room temperature ther-
mistor(RT11)
To disable “Auto restart function”,
solder jumper wire to JR07.
(Refer to 7-3.)
Indoor coil
thermistor(RT13(sub))
R132
Receiver P.C. board
Indoor coil
thermistor(RT12(main))
wThere are 2 types of electronic control P.C. boards
(TYPE1/TYPE2).
They are both compatible with MSZ-A18/24/26YV.
TYPE 1
CN121
Vane motor
power supply
(CN151)
OB345A

19
+
}
}
Resistance (k )
+
{
Fan motor power supply
(CN211)
Fuse (F11)
250 VAC 3.15A
230 VAC
5 VDC
Indoor coil thermistor
(RT12 (main))
Indoor coil thermistor
(RT13 (sub))
Timer short
mode point
(JPS, JPG)
(Refer to 7-1.)
Emergency
operation
switch
CN121
Room temperature
thermistor (RT11)
R132
To disable “Auto restart
function”, solder jumper
wire to JR07.
(Refer to 7-3.)
Vane motor
power supply
(CN151)
12 VDC
Indoor coil thermistor
(RT12 (main), RT13 (sub))
Room temperature thermistor (RT11)
Power supply input
TYPE 2
Receiver P.C. board
CN301
TEST POINT DIAGRAM AND VOLTAGE
MSZ-A18YV - MSZ-A24YV - MSZ-A26YV -
Indoor electronic control P.C. board
E1
E1E1
OB345A

20
DISASSEMBLY INSTRUCTIONS
9
9-1. MSZ-A18YV - MSZ-A24YV - MSZ-A26YV -
NOTE: Turn OFF power supply before disassembly.
E1E1E1
(1) Slide the sleeve and check if there is a locking lever or not. (2) The terminal with this connector is a terminal
with lock mechanism
1Slide the sleeve.
2Pull the terminal while
pushing the locking
lever.
1Hold the sleeve, and
pull out the terminal
slowly.
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.
<"Terminal with lock 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
Screw of the
V.A. clamp
Indoor
electronic
control
P.C. board
Vane motor
connector
Fan motor
connectors
Screws of the earth wire
Screws
Screw of
the electrical
cover
R.L
holder
Screw of
the terminal
block
Receiver
P.C.
board
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 earth 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.
OB345A