Mitsubishi Electric MS-18NV User manual

SERVICE MANUAL
SPLIT-TYPE AIR CONDITIONERS
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. PERFORMANCE CURVES································8
8. MICROPROCESSOR CONTROL ····················10
9. SERVICE FUNCTIONS ····································16
10. TROUBLESHOOTING······································18
11. DISASSEMBLY INSTRUCTIONS·····················24
12. PARTS LIST······················································28
13. OPTIONAL PARTS···········································31
Wireless type
Models
MS-18NV - (WH) · MU-18NV - E4E4
No. OB228
MS-18NV - E4

2
TECHNICAL CHANGES
MS-18NV - ➔MS-18NV -
1. Indoor electronic control P.C. board has changed.
MU-18NV - ➔MU-18NV -
1. Compressor has changed.(NH-33VMDT➔PH-33VPET)
2. Outdoor heat exchanger has changed.
3. Refrigerant filling capacity(R-22) has changed.(1.65kg➔1.05kg)
E4E3
E4E3
1
PART NAMES AND FUNCTIONS
2
INDOOR UNIT
Remote control
receiving section
Air cleaning filter(option)
Deodorizing filter(option)
Grille
(When the grille is open)
MS-18NV - E4

3
TEMPERATURE buttons
Signal transmitting section
Operation display section
OPERATE /STOP
(ON /OFF)button
OPERATION SELECT button
FAN SPEED CONTROL button
SLEEP button
ON-TIMER button
CLOCK SET button
HR. button
MIN. button
(TIME SET button)
VANE CONTROL button
OFF-TIMER button
RESET button
SWING buttons
MS-18NV - E4
OUTDOOR UNIT
MU-18NV - E4
REMOTE CONTROLLER

4
NOTE:Test conditions
Cooling : Indoor DB27:/ WB19:
Outdoor DB35:/ WB24:
SPECIFICATION
3
Capacity
Electrical data
Compressor
Indoor
fan motor
Outdoor
fan motor
Dimensions
Weight
Special remarks
Model
Function
Power supply
Coefficient of performance(C.O.P)
Capacity
Dehumidification
Air flow(Hi)
Power outlet
Running current
Power input
Auxiliary heater
Power factor
Starting current
Compressor motor current
Fan motor current
Model
Output
Winding resistance(at20:)
Model
Winding resistance(at20:)
Model
Winding resistance(at20:)
Indoor unit
Outdoor unit
Indoor unit
Outdoor unit
Air direction
Sound level
(Hi)
Fan speed
(Hi)
Fan speed
regulator
Refrigerant filling capacity(R-22)
Refrigerating oil (Model)
Thermistor
Width
Height
Depth
Width
Height
Depth
Indoor unit
Outdoor unit
Indoor unit
Outdoor unit
Indoor unit
Outdoor unit
RT11(at25:)
RT12(at25:)
kW
R/h
K /h
A
A
W
A(kW)
%
A
A
A
W
"
"

"
mm
mm
mm
mm
mm
mm
kg
kg
dB
dB
rpm
rpm
kg
cc
k"
k"
MS-18NV - E4
Single phase, 220-240V, 50Hz
—
WHT-BLK183.8 BLK-RED250.5
1,015
320
190
850
605
290
14
5
4
10
10
Cooling
5.1
2.5
INDOOR 756 / OUTDOOR 2340-2400
15
9.1
1,910-2,010
95-92
51-55
8.46
INDOOR 0.25 / OUTDOOR 0.39
2.67-2.54
PH-33VPET
1,500
C-R1.08
C-S 2.18
RA4V27-EA or EF
RA6V50-OF or OG
WHT-BLK116.4 BLK-RED111
48
42
52
1,180
830-860
1
1.05
900 (MS32N1)

5
OUTLINES AND DIMENSIONS
4
MS-18NV - E4
MU-18NV - E4
OUTDOOR UNIT
INDOOR UNIT
3 297
450
450
352438
254
20
60
40
150 648 217
5190
995
19077550
320
1015
17.5
160
56
4holes 11o20 Indoor unit
Installation plate
Wireless remote controller
Power supply cord
Lead to right 2m
Lead to left 1m
Wall hole [75
Installation plate
Liquid line [8-0.5m
Gas line [12-0.43m
Insulation [50 O.D
[28 I.D
Insulation [28
Drain hose [16
Air out
{
Air in
If the right/left sides or
back side is vacant,the
front has only to be 50cm
unobstructed.
If the front or right/left sides
are vacant, the top has only
to be 10cm unobstructed.
Unit : mm

6
WIRING DIAGRAM
5
MU-18NV - E4
MODEL WIRING DIAGRAM
OUTDOOR UNIT
NOTE:1. Use copper conductors only.(For field wiring)
2. “w”show the terminals with a lock mechanism, so they cannot be removed when you pull
the lead wire.
Be sure to pull the wire by pushing the locking lever(projected part) of the terminal with a finger.
3. Symbols below indicate.
: Terminal block, : Connector
1.Slide the sleeve.
2.Pull the wire while
pushing the locking
lever.
SYMBOL
C1
C2
SYMBOL
F
MC
SYMBOL
MF
TB
NAME NAME NAME
COMPRESSOR CAPACITOR
OUTDOOR FAN CAPACITOR FUSE(2A)
COMPRESSOR(INNER THERMOSTAT)
OUTDOOR FAN MOTOR(INNER THEMOSTAT)
TERMINAL BLOCK
MS-18NV - E4 MODEL WIRING DIAGRAM
INDOOR UNIT
SYMBOL
RT12
TB
52C
SYMBOL
IC141
MF
MV
NR11
RT11
SYMBOL
C11
DSAR
F11
F12
HIC1
NAME NAME NAME
INDOOR FAN CAPACITOR
SURGE ABSORBER
FUSE(3.15A)
THERMAL FUSE(93¡C)
DC / DC CONVERTER
HYBRID IC
INDOOR FAN MOTOR
VANE MOTOR
VARISTOR
ROOM TEMPERATURE THERMISTOR
INDOOR COIL THERMISTOR
TERMINAL BLOCK
CONTACTOR
NOTE:1. For the outdoor 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
MF
BLK
WHT
RED
ORN
N
220-240V~
BLU 4
BLU
WHT
BLK
RED
C1
TB
WHT
ORN
F
C2 RED
WHT
1
2
3
GRN/YLW
FROM
INDOOR UNIT
CONNECTING
C
SR
MC
2w
w
CIRCUITBREAKER
50Hz
220-240V~
BRN
DSAR
GRN/YLW
LD1
REMOTE
CONTROLLER
3
1
DISPLAY
P.C.BOARD
101
CN 102
CN 151
CN ELECTRONIC CONTROL P.C BOARD
BLU
RECEIVER
P.C.BOARD
MV
5
F11
33
BLU
~/N 220-240V
CORD
POWER
SUPPLY
TO OUTDOOR
UNIT
CONNECTING
BRN
L
N
GRN/YLW
TB
52C
BRN
24
3
CN201
1
2
F12
WHT
BLU
BLU
BLU
TRANS
HIC1
111
CN
4
2
1
C11
CN211
BLK
WHT
GRY
RED
RT11
MF
3
121
CN
CN
112
NR11
IC141 RT12
YLW
BRN
w
w
w
w
w
w

7
REFRIGERANT SYSTEM DIAGRAM
6
MS-18NV - E4 MU-18NV - E4
INDOOR UNIT OUTDOOR UNIT
Indoor
heat
exchanger
Room temperature
thermistor
RT11
Refrigerant pipe [15.88
(Option)
(with heat insulator)
Flared
connection
Indoor coil
thermistor
RT12
Refrigerant pipe [6.35
(Option)
(with heat insulator)
Stop valve Capillary tube
[3.0X[2.0X700
Compressor
Accumulator
Stop valve
(with service port) Outdoor
heat
exchanger
Refrigerant flow in cooling
Strainer
Unit:mm
Distributor
Indoor
unit
w Max. Height
difference 5m
wHeight difference should be within 5m regardless of which unit,
indoor or outdoor position is high.
Outdoor unit
Refrigerant Piping
Max.length
A
Model Outdoor unit precharged
1050
Refrigerant piping length (one way)
15m
120
7m
0
10m
45
MS-18NV - E4
MAX. HEIGHT DIFFERENCE
ADDITIONAL REFRIGERANT CHARGE(R-22 : g)
Model Refrigerant piping
Max. length : m
A
Piping size O.D : mm Length of connecting pipe : m
Indoor unit
Gas 0.43
Liquid 0.5
Gas
15.88
Liquid
6.35
Outdoor unit
Gas 0
Liquid 0
MS-18NV - E4 15
MAX. REFRIGERANT PIPING LENGTH
Calculation : Xg=15g/mO(A-7)m

8
PERFORMANCE CURVES
Wet and dry-bulb
thermometers
Dry-bulb
thermometers
The standard data contained in these specifications apply only to the operation of the air conditioner under normal conditions.
Since operating conditions vary according to the areas where these units are installed. The following information has been
provided to clarify the operating characteristics of the air conditioner under the conditions indicated by the performance curve.
(1) GUARANTEED VOLTAGE
Rated voltage : ±10% (198 ~ 264V),50Hz
(2) AIR FLOW
Air flow should be set at MAX.
(3) MAIN READINGS
(1) Indoor intake air wet-bulb temperature :°CWB
(2) Indoor outlet air wet-bulb temperature :°CWB
(3) Outdoor intake air dry-bulb temperature :°CDB
(4) Total input :W
Indoor air wet-bulb temperature difference on the left side of the chart on next page shows the difference between the
indoor intake air wet-bulb temperature and the indoor outlet air wet-bulb temperature for your reference at service.
How to measure the indoor air wet-bulb temperature difference
1. Attach at least 2 sets of wet-and dry-bulb thermometers to the indoor air intake as shown in the figure, and at least 2 sets
of wet-and dry-bulb thermometers to the indoor air outlet. The thermometers must be attached to the position where air
speed is high.
2. Attach at least 2 sets of dry-bulb thermometers to the outdoor air inlet.
Cover the thermometers to prevent direct rays of the sun.
3. Check that the air filter is cleaned.
4. Open windows and doors of room.
5. Press the EMERGENCY OPERATION switch to start the EMERGENCY operation.
6. When system stabilizes after more than 15 minutes, measure temperature and take an average temperature.
7. 10 minutes later, measure temperature again and check that the temperature does not change.
7
INDOOR UNIT OUTDOOR UNIT
}
Cooling
MS-18NV - E4

9
MS-18NV - E4
11Both indoor and outdoor unit are under the same temperature/humidity condition.
OUTDOOR LOW PRESSURE AND OUTDOOR UNIT CURRENT
COOL operation
22Air flow should be set at MAX.
33The unit of pressure has been changed to MPa on the international system of units(SI unit system).
The conversion factor is : 1(MPa • G) =10.2(kgf/ff• G)
Dry-bulb temperature Relative humidity(%)
20 50
25 60
30 70
15 20
50 25 60 30 70(%) 35(:)
0.3
0.4
0.5
0.6
0.7
7
6
5
4
318 32
220V/240V
15 20
50 25 60 30 70(%) 35(:)
6
7
8
9
10
11
220V/240V
18 32
MU-18NV - E4 MU-18NV - E4
Ambient temperature(˚C)Ambient humidity(%) Ambient temperature(˚C)Ambient humidity(%)
Outdoor low pressure
(kgf/F•G)(MPa•G)
Outdoor unit current(A)

10
Once the operation mode are set, the same operation mode
can be repeated by simply turning the
OPERATE/STOP(ON/OFF) button ON.
Indoor unit receives the signal with a beep tone.
When the system turns off, 3-minute time delay will operate to
protect system from overload and compressor will not restart
for 3 minutes.
8-1. “I FEEL CONTROL” ( ) OPERATION
(1) Press OPERATE/STOP(ON/OFF) button on the remote
controller. Operation Indicator lamp of the indoor unit
turns on with a beep tone.
(2) Select “I FEEL CONTROL”( ) mode with the
OPERATION SELECT button.
(3) The operation mode is determined by the room
temperature at start-up of the operation.
MICROPROCESSOR CONTROL
8
lighting
not lighting
About 2 : 
or more
Difference
betweeen set
temperature
and room
temperature
About 2 : 
or less
This shows that the
air conditioner is
operating to reach
the target temperature.
Please wait unitil the
target temperature is
obtained.
This shows that the
room temperature is
approaching the
target temperature.
Operation state
Indication
Operation Indicator
Operation Indicator lamp
The operation indicator at the right side of the indoor
unit indicates the operation state.
INDOOR UNIT DISPLAY SECTION
Example
Previous operation
COOL mode of
“I FEEL CONTROL” or
COOL mode
● Once the mode is fixed, the mode does not change by
room temperature afterwards.
● Under the ON-TIMER ( ) operation, the mode is
determined according to the room temperature as the
operation starts.
● When the system is stopped with the
OPERATE/STOP(ON/OFF) button on the remote
controller, and restarted within 2 hours in “I FEEL
CONTROL” ( ) mode, the system operates in previous
mode automatically regardless of the room temperature.
Example
Previous operation
COOL mode of
“I FEEL CONTROL”
or COOL mode
When the system is restarted after 2 hours and more,
the operation mode is determined by the room
temperature at start-up of the operation.
Restart
COOL mode of
“I FEEL CONTROL”
Restart
COOL or DRY mode of
“I FEEL CONTROL” that
determined by room
temperature at start-up
of the operation.
MS-18NV - E4
TEMPERATURE buttons
Signal transmitting section
Operation display section
OPERATE /STOP
(ON /OFF)button
OPERATION SELECT button
FAN SPEED CONTROL button
SLEEP button
ON-TIMER button
CLOCK SET button
HR. button
MIN. button
(TIME SET button)
VANE CONTROL button
OFF-TIMER button
RESET button
SWING buttons
Initial room temperature
25:or more
more than 13:,
less than 25:
mode
COOL mode of
“I FEEL CONTROL“
DRY mode of
“I FEEL CONTROL”
WIRELESS REMOTE CONTROLLER

11
Mode
COOL mode of
"I FEEL CONTROL"
DRY mode of
"I FEEL CONTROL"
Initial room temperature Initial set temperature
26:or more
25:to 26:
more than13:, less than 25:
24:
Initial room temperature
minus 2:
Initial room temperature
minus 2:
w1
w1 When the system is restarted with the remote controller, the system operates with the previous set temperature
regardless of the room temperature at restart.
The set temperature is calculated by the previous set temperature.
(5) TEMPERATURES buttons
In “I FEEL CONTROL” ( ) mode, set temperature is decided by the microprocessor based on the room temperature.
In addition, set temperature can be controlled by TOO WARM or TOO COOL buttons when you feel too cool or too warm.
Each time the TOO WARM or TOO COOL button is pressed, the indoor unit receives the signal and emits a beep tone.
● Fuzzy control
When the TOO COOL or TOO WARM button is pressed, the microprocessor changes the set temperature, considering
the room temperature, the frequency of pressing TOO COOL or TOO WARM button and the user’s preference to heat or
cool. So this is called “Fuzzy control”, and works only in “I FEEL CONTROL” mode.
In DRY mode of “I FEEL CONTROL”, the set temperature doesn’t change.
▲ TOO
COOL … To raise the set temperature 1~2 degrees(°C)
▼ TOO
WARM … To lower the set temperature 1~2 degrees(°C)
(4) The initial set temperature is decided by the initial room temperature.
1. Indoor fan speed control
Indoor fan operates at the set speed by FAN SPEED CONTROL button.
In Auto the fan speed is as follows. Initial temperature difference
Room temperature minus set temperature : 2 degrees or more········································Hi
Room temperature minus set temperature : Between 1 and 2 degrees····························Me
Room temperature minus set temperature : less than 1 degree·······································Lo
2. Coil frost prevention
1Temperature control
When the indoor coil thermistor RT12 reads -1°C or below, the coil frost prevention mode starts immediately.
However, the coil frost prevention doesn’t work after 5 minutes since the compressor has started.
Indoor fan operates at the set speed and the compressor stops for 5 minutes.
After that, if RT12still reads below -1°C this mode is prolonged until the RT12 reads over -1°C.
2Time control
When the three conditions as follows have been satisfied for 1 hour and 45 minutes, compressor stops for 3 minutes.
a. Compressor has been continuously operating.
b. Indoor fan speed is Lo or Me.
c. Room temperature is below 26°C.
When compressor stops, the accumulated time is cancelled and when compressor restarts, time counting starts
from the beginning.
Time counting also stops temporarily when the indoor fan speed becomes Hi or the room temperature exceeds
26°C. However, when two of the above conditions (b.and c.) are satisfied again.Time accumulation is resumed.
1 deg. 1.7 deg.
2 deg. 4 deg.
— COOL mode of “I FEEL CONTROL” —
Fan speed Difference between room
temperature and set
temperature during

12
Compressor
Outdoor fan OFF
ON
(continuously at set speed)
Indoor fan ON
ON
OFF
—DRY mode of “I FEEL CONTROL”—
The system for dry operation uses the same refrigerant circuit as the cooling circuit.
The compressor and the indoor fan are controlled by the room temperature.
By such controls, indoor flow amounts will be reduced in order to lower humidity without much room temperature
decrease.
1. Indoor fan speed control
Indoor fan operates at the set speed by FAN SPEED CONTROL button.
However, in AUTO fan operation, fan speed becomes Lo.
2. The operation of the compressor and indoor fan/ outdoor fan
Compressor operates by room temperature control and time control.
Set temperature is controlled to fall 2°C from initial room temperature.
Indoor fan and outdoor fan operate in the same cycle as the compressor.
• When the room temperature is 23°C or over:
When the thermostat is ON, the compressor repeats 8 minutes ON and 3 minutes OFF.
When the thermostat is OFF, the compressor repeats 4 minutes OFF and 1 minute ON.
• When the room temperature is under 23°C.
When the thermostat is ON, the compressor repeats 2 minutes ON and 3 minutes OFF.
When the thermostat is OFF, the compressor repeats 4 minutes OFF and 1 minute ON.
Operation time chart
Example
3. Coil frost prevention
• The operation is as same as coil frost prevention during COOL mode of “I FEEL CONTROL”.
• Indoor fan operates at the set speed and the compressor stops for 5minutes, because protection (Coil frost prevention)has
the priority. However when coil frost prevention works while the compressor is not operating, it’s speed becomes Lo.
Thermostat
Indoor fan
Outdoor fan
compressor
1st ON
8 min. 1 min.
3 min.
2nd ON
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
ON
ON
ON
Operation chart
Example

13
8-2. COOL ( ) OPERATION
(1) Press OPERATE/STOP(ON/OFF) button.
Operation Indicator lamp of the indoor unit
turns on with a beep tone.
(2) Select COOL mode with the OPERATION
SELECT button.
(3) Press the TEMPERATURES button.
(TOO WARM or TOO COOL button) to select
the desired temperature.
The setting range is 16 ~ 31°C.
wIndoor fan continues to operate regardless
of thermostat’s OFF-ON at set speed.
wCoil frost prevention is as same as COOL
mode of “I FEEL CONTROL”.
8-3. DRY ( ) OPERATION
(1) Press OPERATE/STOP(ON/OFF) button.
Operation Indicator lamp of the indoor unit
turns on with a beep tone.
(2) Select DRY mode with the OPERATION
SELECT button.
(3) The microprocessor reads the room
temperature and determines the set
temperature. Set temperature is as shown on
the right chart.
Thermostat (SET TEMP.)does not work.
The other operations are same as DRY
mode of “I FEEL CONTROL”.
(4) DRY operation will not function when the room temperature is 13°C or below.
(5) When DRY operation functions, the fan speed is lower than cool operation.
SLEEP
8-5. FAN MOTOR CONTROL
(1) Rotational frequency feedback control
The indoor fan motor is equipped with a rotational frequency sensor, and outputs signal to the microprocessor to
feedback the rotational frequency. Comparing the current rotational frequency with the target rotational frequency
(Hi,Me,Lo,SLEEP), the microprocessor controls IC141 and adjusts fan motor electric current to make the current
rotational frequency close to the target rotational frequency. With this control, when the fan speed is switched, the
rotational frequency changes smoothly.
(2) Fan motor lock-up protection
When the rotational frequency feedback signal has not output for 12 seconds, (or when the microprocessor cannot
detect the signal for 12 seconds) the fan motor is regarded locked-up. Then the electric current to the fan motor is shut
off. 3 minutes later, the electric current is applied to the fan motor again. During the fan motor lock-up, the Operation
Indicator lamp flashes on and off to show the fan motor abnormality. (See page 19.)
8-4.FAN( d )OPERATION
(1) Press OPERATE/STOP(ON/OFF) button.
(2) Select FAN mode with the OPERATION SELECT button.
(3) Select the desired fan speed.When AUTO, it becomes Lo.
Only indoor fan operates.Outdoor unit does not operate.
8-6. AUTO VANE OPERATION
(1) Vane motor drive
These models are equipped with a stepping motor for the horizontal vane. The rotating direction, speed, and angle of
the motor are controlled by pulse signals (approx. 12V) transmitted from indoor microprocessor.
(2) The horizontal vane angle and mode changes as follows by pressing the VANE CONTROL ( ) button.

14
(3) Positioning
The vane is once pressed to the vane stopper below to confirm the standard position and then set to the desired angle.
Confirming of standard position is performed in case of follows.
(a) When the OPERATE/STOP(ON/OFF) button is pressed.
(b) When the vane control is changed from AUTO to MANUAL.
(c) When the SWING is finished.
(d) When the test run starts.
(e) When the power supply turns ON.
(4) VANE AUTO ( ) mode
In VANE AUTO mode, the microprocessor automatically determines the vane angle and operation to make the optimum
room-temperature distribution.
(5) Dew prevention
During COOL or DRY operation at Vane Angle 4 or 5 when the compressor cumulative operation time exceeds 1 hour,
the vane angle automatically changes to Angle 1 for dew prevention.
(6) SWING MODE ( )
By pressing the SWING button ( ),the horizontal vane swings vertically. The remote controller displays “ ”. SWING
mode is cancelled when the SWING button or VANE CONTROL button ( ) is pressed the mode is changed.
1In COOL and DRY operation
2In FAN operation
Vane angle is fixed to Angle 1.
Vane angle is fixed to Angle 4.
8-7. SLEEP MODE ()
• When the SLEEP button ( ) is pressed, the indoor fan speed drops and the air flow sound from the indoor unit is
decreased.
• The indications of the remote controller are “ ” and “ ”.
• When the FAN SPEED CONTROL button ( ) or the SLEEP button ( ) or mode change button is pressed during the
SLEEP mode, the SLEEP mode is released.
8-8. TIMER OPERATION
1. How to set the timer
(1) Press OPERATE/STOP(ON/OFF) button to start the air conditioner.
(2) Check that the current time is set correctly.
NOTE : Timer operation will not work without setting the current time. Initially “AM0:00” blinks at the current time display of
TIMER MONITOR, so set the current time correctly with CLOCK SET button.
(3) Press TIMER CONTROL button to select the operation.
“ ” button... AUTO START operation (ON timer)
“ ” button... AUTO STOP operation (OFF timer)
(4) Press HR. and MIN. button to set the timer. Time setting is 10-minute units.
HR. and MIN. button will work when “ ” or “ ” mark is flashing.
These marks disappear in 1 minute.
After setting the ON timer, check that Operation Indicator lamp of the indoor unit lights.
NOTE1 : Be sure to place the remote controller at the position where its signal can reach the air conditioner even during
TIMER operation, or the set time may deviate within the range of about 10 minutes.
NOTE2 : Reset the timer in the following cases, or the set time may deviate and other malfunctions may occur.
● A power failure occurs.
● The circuit breaker functions.

15
2. Cancel
Timer setting can be cancelled with the TIMER CONTROL buttons. (“ ” or “ ”)
To cancel the ON timer, press the “ ” button.
To cancel the OFF timer, press the “ ” button.
Timer is cancelled and the display of set time disappears.
PROGRAM TIMER
(Example 1) The current time is 8:00 PM.
The unit turns off at 11:00 PM, and on at 6:00 AM.
● The OFF timer and ON timer can be used in combination.
● “ ”and “ ” display shows the order of the OFF timer and ON timer operation.
(Example 2) The current time is 11:00 AM.
The unit turns on at 5:00 PM, and off at 9:00 PM.
NOTE : TIMER setting will be cancelled by power failure or breaker functioning.
8-9. EMERGENCY-TEST OPERATION
When the remote controller is missing, has failed or when the batteries run down, press the EMERGENCY OPERATION
switch on the front of the indoor unit. The unit will start and the Operation Indicator lamp will light.
The first 30 minutes of operation is the test run operation. This operation is for servicing. The indoor fan speed runs at
high notch and the system is in continuous operation. (The thermostat is ON.)
After 30 minutes of test run operation the system shifts to EMERGENCY COOL MODE with a set temperature of 24°C.
The fan shifts to Me notch.
This operation continues until the EMERGENCY OPERATION switch is pressed again or the unit receives any signal
from the remote controller. In case of latter normal operation will start.
The coil frost prevention works even in this operation.
In the test run or Emergency operation, the horizontal vane operates in VANE AUTO mode.
NOTE : Do not press the EMERGENCY OPERATION switch during normal operation.
EMERGENCY OPERATION switch
Press once <Cool>
Press again <Stop>
Operation Indicator lamp

SERVICE FUNCTIONS
16
9
9-2. P.C. BOARD MODIFICATION FOR INDIVIDUAL OPERATION
A maximum of 4 indoor units with wireless remote controllers can be used in a room.
In this case, to operate each indoor unit individually by each remote controller, P.C. boards of remote controller must be
modified according to the number of the indoor unit.
9-1. TIMER SHORT MODE
For service, set time can be shortened by short circuit of JPG and JPS on the electronics control P.C. board.
The time will be shortened as follows.
3-minutes delay : 3-minutes ➔ 3-seconds.
AUTO START : 1 hour ➔ 1-minute
AUTO STOP : 1 hour ➔ 1-minute Short the connector during the timer mode.
}
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”. Jumper wires are mounted to each “J1” and “J2”. Cut J1 and J2 according
to the number of indoor unit as shown in Table 1..
After modification,push the reset button.
NOTE : For remodelling, take out
the batteries at first.
After finish remodelling, put
back the batteries then
push the RESET button.
No. 1 unit
No. 2 unit
No. 3 unit
No. 4 unit
1 unit operation
No modification
–
–
–
2 units operation
Same as at left
Cut J1
–
–
3 units operation
Same as at left
Same as at left
Cut J2
–
4 units operation
Same as at left
Same as at left
Same as at left
Cut both J1 and J2
Table 1.
NOTE :
At power supply failure or installation, indoor unit deletes the memory about remote controller. When the power supply
is turned on and indoor unit receives the first signals from the remote controller, the remote controller number is
designated as the indoor unit number. Therefore at and after the second time indoor unit accepts the remote controller
of the initial setting number.
At setting-error, turn the power supply off to cancel the individual operation, and then turn the power supply on to
restart the setting.
MS-18NV - E4

17
9-3. 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 operation is
decided by the initial room temperature.
How to set “AUTO RESTART FUNCTION”
1Turn off the main power for the unit.
2Remove the electronic control P.C. board and the display P.C.board.(See page 24.)
3Cut the RESISTOR JR06 on the indoor electronic control P.C.board.
JR06
CN102
CN151
CN112 CN111 CN121
CN101
BZ
SW
52C
IC101 RA102
IC141
CN211
C11CN201
Operation
1If the main power (220/240V AC) 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 under the same power system,compressor starting current as large
as that for all the compressors used flows at a time as soon as the units restart automatically.
Therefore, the specific counter-measures are required to prevent main voltage drop or the rush of starting current by
providing the system to allow the units to start in regular succession.

18
10 TROUBLESHOOTING
10-1. Cautions on troubleshooting
1. Before troubleshooting, check the following:
1) Check the power supply voltage.
2) Check the indoor/outdoor connecting wire for mis-wiring.
2. Take care the following during servicing.
1) Before servicing the air conditioner, be sure to first turn off the remote controller to stop the unit, and then after
confirming the horizontal vane is closed, turn off the breaker and / or disconnect the power plug.
2) When removing the electronic control P.C. board, hold the edge of the board with care NOT to apply stress on the
components.
3) 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 the abnormality indication for 2 or 3 times before starting service work.
2) If the electronic control P.C. board is supposed to be defective, check the copper foil pattern for disconnection and
the components for bursting and discoloration.
3) When troubleshooting, refer to the flow chart and the check table on page 19.
4. How to replace batteries
Weak batteries may cause the remote controller malfunction.
In this case, the remote controller can not be repaired only by the battery replacement. To operate the remote
controller normally, discharge the remote controller in the following order.
This remote controller has the RESET button. After refilling new batteries, press the RESET button with tip end of ball
point pen or the like, and then use the remote controller.
MS-18NV - E4
RESET button

19
10-2. Instruction of troubleshooting
Indoor unit
operates. Outdoor
unit doesn’t
Outdoor unit
operates in
only Test
Run
operation.
Outdoor unit
doesn’t
operate even
in Test Run
operation.
Check room
temperature
thermistor.
Refer to
“Check of
outdoor unit”
on page 22.
Indoor unit doesn’t
receive the signal
from remote
controller.
Refer to “Check
of remote controller
and receiver P.C.
board” on page 21.
Operation Indicator lamp
on the indoor unit is
flashing on and off.
Indoor unit doesn’t
receive the signal from
remote controller.
Also, Operation Indicator
lamp doesn’t flash, when
the EMERGENCY
OPERATION switch is
pressed.
Refer to “Check of
indoor electronic control
P.C. board” on page 22.
Cause:Indoor unit
2-time-Room temperature/Indoor coil thermistor trouble
3-time-Indoor fan motor trouble
D
B
Check room temperature
thermistor. Refer to“Test
point diagram and
voltage” on page 23.
Refer to
“Check of indoor
fan motor” on
page 21.
Check indoor coil
thermistor. Refer
to“Test point
diagram and
voltage” on page
23.
2-time flash
2.5-second OFF
3-time flash
2.5-second OFF
Start
C
A
1. troubleshooting check table
Operation Indicator
wBefore taking measures, make sure that the symptom reappears for accurate troubleshooting.
Self check table
NO.
1
2
Abnormal
point
Indoor coil
thermistor
Room
temperatur
e
thermistor
Indoor fan
motor
Indication
2-time flash
2.5-second OFF
3-time flash
2.5-second OFF
Symptom
Outdoor unit
does not run.
Indoor fan motor
repeats 12
seconds ON and
3 minutes OFF.
When the indoor
fan motor
breaks, the fan
keeps stopping.
Detect method
Detect Indoor coil/room
temperature thermistor short
or open circuit every 8
seconds during operation.
When rotational frequency
feedback signal is not emit
during 12-second indoor fan
operation
Check point
● Check thermistor calibration.
● Reconnect connector.
● Check indoor electronic control P.C.
board.
● Disconnect connector CN211 and then
check connector CN121 2- 3to 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.

20
Measure the resistance between the terminals with a tester.
(Coil wiring temperature –10°C ~ 40°C)
Measure the resistance between the terminals with a tester.
(Coil wiring temperature –10°C ~ 40°C)
Measure the resistance between the terminals with a tester.
(Coil wiring temperature10°C ~ 30°C)
Compressor
Room
temperature
thermistor
2. Trouble criterion of main parts
Part name
Indoor coil
thermistor
Indoor fan
motor
Motor part
Sensor part
Outdoor fan
motor
Vane motor
Check method and criterion
Measure the resistance with a tester.
(Part temperature 10°C ~ 30°C)
Measure the voltage Power ON.
Measure the resistance between the terminals with a tester.
(Part temperature10°C ~ 30°C)
Figure
P~
BLK
R
MAIN
AUX
RED
S
C
WHT
MAIN
AUX
FUSE
BLK
RED
WHT
GRY
YLW BRN
MAIN
AUX
BLK RED WHTORN
P
YLW
RED
BLU
ORN
PNK
ROTOR
INNER PROTECTOR
P
Normal
8k½~ 20k½
Abnormal
Opened or short-circuited
Normal
0.95 ~ 1.17½
1.92 ~ 2.36½
C-R
C-S
Normal Abnormal
Opened or
short-circuited
176 ~ 192½
240 ~ 261½
WHT-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.)
Normal Abnormal
Opened or
short-circuited
WHT-BLK
BLK-RED
Normal Abnormal
Opened or short-circuited
358 ~ 388½
Abnormal
Opened or
short-circuited
MS-18NV - E4
102 ~ 126½
97.9 ~ 120½