Mitsubishi Electric MSZ-HM09NA-U1 User manual

Outdoor unit service manual
MUZ-HM•NA Series (OBH747)
NOTE:
RoHS compliant products have <G> mark on the spec name plate.
PARTS CATALOG (OBB746)
MSZ-HM24NA
INDOOR UNIT
SERVICE MANUAL
INDOOR UNIT
Models
MSZ-HM09NA -U1
MSZ-HM12NA -U1
MSZ-HM15NA -U1
MSZ-HM18NA -U1
MSZ-HM24NA -U1
CONTENTS
1. TECHNICAL CHANGES······································· 2
2. PART NAMES AND FUNCTIONS·····················3
3. SPECIFICATION················································5
4. OUTLINES AND DIMENSIONS ························7
5. WIRING DIAGRAM············································ 8
6. REFRIGERANT SYSTEM DIAGRAM···············9
7. SERVICE FUNCTIONS ···································10
8. MICROPROCESSOR CONTROL ···················12
9. TROUBLESHOOTING·····································16
10. DISASSEMBLY INSTRUCTIONS···················· 30
No. OBH746
REVISED EDITION-B
Please void OBH746 REVISED EDITION-A.
Revision B:
• 3-1. OPERATING RANGE has been modified.

2
1TECHNICAL CHANGES
MSZ-HM24NA - U1
1. New model
MSZ-HM09NA - U1
MSZ-HM12NA - U1
MSZ-HM15NA - U1
MSZ-HM18NA - U1
1. New model
Use the speci¿ed 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:
• MSZ-HM09/12/15/18NA- U1 have been added.
Revision B:
• 3-1. OPERATING RANGE has been modified.
OBH746B

3
2PART NAMES AND FUNCTIONS
MSZ-HM09NA MSZ-HM12NA MSZ-HM15NA
Operation indicator lamp
Remote control receiving section
Emergency operation switch
Horizontal vane
Air outlet
Air ¿lter
Air inlet
Heat exchanger
Front panel
Air cleaning ¿lter
(Anti-Allergy Enzyme
Filter, option)
Display section Remote controller
ACCESSORIES
Installation plate 1
Attachment screws for the installation plate
4 × 25 mm 5
Battery (AAA) for remote controller 2
Wireless remote controller 1
Felt tape (For left or left-rear piping) 1
OBH746B

4
MSZ-HM18NA MSZ-HM24NA
ACCESSORIES
Installation plate 1
Attachment screws for the installation
plate 4 × 25 mm 5
Wireless remote controller 1
Felt tape (For left or left-rear piping) 1
Battery (AAA) for remote controller 2
Remote controller
Operation indicator lamp
Remote control receiving section
Emergency operation switch
Horizontal vane
Air outlet
Air ¿lter
Air inlet
Heat exchanger
Front panel
Air cleaning ¿lter
(Anti-Allergy Enzyme
Filter, option)
Display section
OBH746B

5
3SPECIFICATION
Indoor model MSZ-HM18NA MSZ-HM24NA
Power supply V, phase, Hz 208/230, 1, 60
Max. fuse size (time delay)/ Disconnect switch A15
Min. circuit ampacity A 1.0
Fan motor F.L.A 0.67
AirÀow
Super High - High - Med. -
Low
COOL Dry
(Wet)
CFM 625 - 530 - 431 - 328
(562 - 477 - 388 - 295) 702 - 530 - 431 - 353 (632 - 477 - 388 - 318)
HEAT Dry CFM 625 - 530 - 431 - 307 702 - 579 - 448 - 346
Moisture removal pt./h 2.1 2.3
Sound level
Super High - High - Med. -
Low
Cooling dB(A) 47 - 42 - 37 - 30 50 - 44 - 38 - 33
Heating dB(A) 47 - 42 - 37 - 30 50 - 44 - 38 - 32
Fan speed
Super High - High - Med. -
Low
Cooling rpm 1,140 - 1,000 - 850 - 690 1,250 - 1,000 - 850 - 730
Heating rpm 1,140 - 1,000 - 850 - 660 1,250 - 1,070 - 880 - 720
Cond. drain connection O.D. in. 5/8
Dimensions Win. 36-5/16 D9-13/16
H12
Weight Ib. 28
External ¿nish Munsell 1.0Y 9.2/0.2
Control voltage (by built-in transformer) 12 - 24 VDC
NOTE: Test conditions are based on AHRI 210/240.
Indoor model MSZ-HM09NA MSZ-HM12NA MSZ-HM15NA
Power supply V, phase, Hz 208/230, 1, 60
Max. fuse size (time delay)/ Disconnect switch A15
Min. circuit ampacity A 1.0
Fan motor F.L.A 0.76
AirÀow
Super High - High - Med. -
Low
COOL Dry
(Wet)
CFM 399 - 321 - 237 - 170
(364 - 286 - 201 - 134) 533 - 420 - 335 - 272 (498 - 385 - 300 - 237)
HEAT Dry CFM 406 - 321 - 237 - 170 463 - 367 - 304 - 247
Moisture removal pt./h 1.5 2.5 2.7
Sound level
Super High - High - Med. -
Low
Cooling dB(A) 43 - 37 - 30 - 22 45 - 37 - 30 - 22 49 - 44 - 38 - 32
Heating dB(A) 43 - 37 - 30 - 22 46 - 40 - 35 - 30
Fan speed
Super High - High - Med. -
Low
Cooling rpm 1,020 - 860 - 670 - 530 1,280 - 1,060 - 880 - 740
Heating rpm 1,040 - 860 - 670 - 530 1,140 - 950 - 810 - 690
Cond. drain connection O.D. in. 5/8
Dimensions Win. 31-7/16 D9-1/8
H11-5/8
Weight Ib. 22
External ¿nish Munsell 1.0Y 9.2/0.2
Control voltage (by built-in transformer) 12 - 24 VDC
NOTE: Test conditions are based on AHRI 210/240.
OBH746B

6
(2) OPERATION
Mode Condition Intake air temperature (°F) Indoor Outdoor
DB WB DB WB
Cooling
Standard temperature 80 67 95 —
Maximum temperature 90 73 115 —
Minimum temperature 67 57 14 —
Maximum humidity 78% —
Heating Standard temperature 70 60 47 43 Maximum temperature 80 67 75 65
Minimum temperature 70 60 -4(NA), 5(NA2)-5(NA), 4 (NA2)
3-1. OPERATING RANGE
(1) POWER SUPPLY
Rated voltage Guaranteed voltage (V)
Indoor unit 208/230 V 1 phase
60 Hz
Min. 187 208 230 Max. 253
3-2. OUTLET AIR SPEED AND COVERAGE
ƔThe air coverage is the figure up to the
position where the air speed is 1 ft./s.,
when air is blown out horizontally from
the unit properly at the High speed posi-
tion.
The coverage should be used only as a
general guideline since it varies accord-
ing to the size of the room and furniture
arranged inside the room.
Model Mode Function AirÀow
(CFM) Air speed (ft./s.) Coverage (ft.)
MSZ-HM09NA HEAT Dry 406 20.6 29.5
COOL Dry 321 16.3 23.5
Wet 286 14.5 21.0
MSZ-HM12NA HEAT Dry 406 20.6 29.5
COOL Dry 321 16.3 23.5
Wet 286 14.5 21.0
MSZ-HM15NA HEAT Dry 463 23.4 33.5
COOL Dry 420 21.3 30.5
Wet 385 19.5 28.0
MSZ-HM18NA HEAT Dry 625 28.5 42.6
COOL Dry 625 28.5 42.6
Wet 562 25.6 38.4
MSZ-HM24NA HEAT Dry 702 32.0 47.7
COOL Dry 702 32.0 47.7
Wet 632 28.8 43.1
OBH746B

7
Unit: inch
MSZ-HM09NA MSZ-HM12NA MSZ-HM15NA
MSZ-HM18NA MSZ-HM24NA
4OUTLINES AND DIMENSIONS
Piping
Insulation
MSZ-HM24NA
Ø2 O.D
Liquid line Ø5/16 15-3/8 (Flared connection Ø3/8)
Gas line Ø15/32 13-3/8 (Flared connection Ø5/8)
Drain hose
Insulation Ø1-1/8 Connected part Ø5/8 O.D
Piping
Insulation
MSZ-HM18NA
Ø2 O.D
Liquid line Ø5/16 15-3/8 (Flared connection Ø1/4)
Gas line Ø15/32 13-3/8 (Flared connection Ø1/2)
Drain hose
Insulation Ø1-1/8 Connected part Ø5/8 O.D
11/16
5-1/2
2-1/4
2-1/4
2-1/2
9-13/16
3/16
35-13/16
36-5/16
1/4
27-15/16 6-5/16
2-1/16
12
2-9/16
2-13/16
2-1/2
2-9/16
3-11/16
2-1/16
9-7/16
10-5/16
1/8
8-7/8 8-7/8 3-11/16
8-3/4
10-3/8
2-5/16 15-7/8
8-11/16
3-11/16
7/8
1×7/16 Oblong hole
7/16×13/16
Oblong hole
Installation plate
Indoor unit
Wall hole Ø3
Air in
Installation plate
8-1/16
15-3/16
1-5/8
8-11/16
3
1-11/16
2-9/16
2-9/16
4-1/2
5-3/4
1/4
Air out
Piping
Drain hose
3-15/16
11/16
5-1/2
2-1/4
Piping
Insulation ø1 - 3/8 O.D
Liquid line ø1/4 19 - 11/16 (Flared connection ø1/4)
Gas line ø3/8 16 - 15/16
(Flared connection: ø3/8 (HM09/12NA), ø1/2 (HM15NA))
Drain hose Insulation ø1-1/8 O.D Connected part ø5/8 O.D
OBH746B

8
MSZ-HM18NA MSZ-HM24NA
5WIRING DIAGRAM
MSZ-HM09NA MSZ-HM12NA MSZ-HM15NA
OBH746B

9
MSZ-HM18NA MSZ-HM24NA
Unit: inch (mm)
Indoor
heat
exchanger
Flared connection
Room temperature
thermistor
RT11
Flared connection
Refrigerant pipe ø1/2 (ø12.7) (MSZ-HM18NA)
ø5/8 (ø15.88) (MSZ-HM24NA)
(with heat insulator)
Refrigerant pipe ø1/4 (ø6.35) (MSZ-HM18NA)
ø3/8 (ø9.52) (MSZ-HM24NA)
(with heat insulator)
Indoor coil
thermistor
RT12 (main)
Indoor coil
thermistor
RT13 (sub)
Refrigerant flow in cooling
Refrigerant flow in heating
6REFRIGERANT SYSTEM DIAGRAM
Indoor
heat
exchanger
Flared connection
Room temperature
thermistor
RT11
Flared connection
Refrigerant pipe ø3/8 (ø9.52) (MSZ-HM09/12NA)
ø1/2 (ø12.7) (MSZ-HM15NA)
(with heat insulator)
Refrigerant pipe ø1/4 (ø6.35)
(with heat insulator)
Indoor coil
thermistor
RT12 (main)
Indoor coil
thermistor
RT13 (sub)
Refrigerant flow in cooling
Refrigerant flow in heating
MSZ-HM09NA MSZ-HM12NA MSZ-HM15NA
OBH746B

10
7-1. TIMER SHORT MODE
For service, the set time can be shortened by bridging of the timer short point on the indoor electronic control P.C. board.
The time will be shortened as follows. (Refer to 9-7.)
• The set time for the ON/OFF timer can be reduced to 1 second for each minute.
• After the breaker is turned on, the time for starting the compressor, which normally takes 3 minutes, can be reduced to
3 seconds. Restarting the compressor, which takes 3 minutes, cannot be reduced.
7-2. REMOTE CONTROLLER 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, the remote controller P.C. boards 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:
7SERVICE FUNCTIONS
MSZ-HM09NA MSZ-HM12NA MSZ-HM15NA MSZ-HM18NA MSZ-HM24NA
J2
J1
The remote controller 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 STOP/
OPERATE (OFF/ON) button 2
or 3 times at first.
After finish modification, put
back the batteries then press
the RESET button.
Table 1
1 unit operation 2 units operation 3 units operation 4 units operation
No. 1 unit No modi¿cation Same as at left Same as at left Same as at left
No. 2 unit — Solder J1 Same as at left Same as at left
No. 3 unit — — Solder J2 Same as at left
No. 4 unit — — — Solder both J1 and J2
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 is turned OFF, or the power supply is shut down.
Please conduct the above setting once again after the power has been restored.
OBH746B

11
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 turned 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 the breaker from tripping OFF due to the rush of starting current, systematize other home appliance not to
turn ON at the same time.
• When some air conditioners are connected to the same supply system, if they are operated before power failure, the
starting current of all the compressors may flow simultaneously at restart.
Therefore, the special counter-measures are required to prevent the main voltage-drop or the rush of the starting
current by adding to the system that allows the units to start one by one.
7-3. AUTO RESTART FUNCTION
When the indoor unit is controlled with the remote controller, the operation mode, the 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 shut-off of the main power.
Operation
If the main power has been cut, the operation settings remain.
After the power is restored, the unit restarts automatically according to the memory.
(However, it takes at least 3 minutes for the compressor to start running.)
How to disable “AUTO RESTART FUNCTION”
Turn OFF the main power of the unit.
Solder the Jumper wire JR07 on the indoor electronic control P.C. board. (HM09/12/15NA)
Cut the Jumper wire JR77 on the indoor electronic control P.C. board. (HM18/24NA) (Refer to 9-7.)
JR77
Indoor electronic
control P.C. board
CN10ACN111
CN151
CN112
CN110
MSZ-HM18/24NA
CN111CN112
CN151
CN10A
Indoor electronic
control P.C. board
JR07
MSZ-HM09/12/15NA
OBH746B

12
WIRELESS REMOTE CONTROLLER
NOTE: Last setting will be stored after the unit is turned OFF with the remote controller. Indoor unit receives the signal of the
remote controller with beeps.
8MICROPROCESSOR CONTROL
MSZ-HM09NA MSZ-HM12NA MSZ-HM15NA MSZ-HM18NA MSZ-HM24NA
Fan speed control button
Operation select button
Timer mode select button
Time set buttons
RESET button
Vane control button
Temperature buttons
ECONO COOL button
Signal transmitting section
Operation display section
OFF/ON (stop/operate) button
Operation Indicator lamp
The operation indicator at the right side of the indoor unit indicates the operation state.
•The following indication applies regardless of shape of the indication.
Indication Operation state Room temperature
The unit is operating to
reach the set temperature About 4°F (2°C) or more away from set temperature
The room temperature is
approaching the set tem-
perature About 2 to 4 °F (1° to 2°C)
from set temperature
Lighted
Blinking
Not lighted
8-1. COOL ( ) OPERATION
(1) Press STOP/OPERATE (OFF/ON) button.
OPERATION INDICATOR lamp of the indoor unit turns on with a beep tone.
(2) Select COOL mode with OPERATION SELECT button.
(3) Press TEMPERATURE buttons (TOO WARM or TOO COOL button) to select the desired temperature.
The setting range is 61 - 88°F (16 - 31°C).
1. Coil frost prevention
The compressor operational frequency is controlled by the temperature of the indoor heat exchanger to prevent the coil
from frosting.
When the temperature of indoor heat exchanger becomes too low, the coil frost prevention mode works. The indoor fan
operates at the set speed and the compressor stops. This mode continues until the temperature of indoor heat exchanger
rises.
INDOOR UNIT DISPLAY SECTION
OBH746B

13
8-2. DRY ( ) OPERATION
(1) Press STOP/OPERATE (OFF/ON) button.
OPERATION INDICATOR lamp of the indoor unit turns on with a beep tone.
(2) Select DRY mode with OPERATION SELECT button.
(3) The set temperature is determined from the initial room temperature.
1. Coil frost prevention
Coil frost prevention works the same way as that in COOL mode. (8-1.1.)
8-3. HEAT ( ) OPERATION
(1) Press STOP/OPERATE (OFF/ON) button.
OPERATION INDICATOR lamp of the indoor unit turns on with a beep tone.
(2) Select HEAT mode with OPERATION SELECT button.
(3) Press TEMPERATURE buttons (TOO WARM or TOO COOL button) to select the desired temperature.
The setting range is 61 - 88°F (16 - 31°C).
1. Cold air prevention control
When the compressor is not operating or is starting, and the temperature of indoor heat exchanger and/or the room tem-
perature is low or when defrosting is being done, the indoor fan will stop or rotate in Very Low speed.
2. High pressure protection
The compressor operational frequency is controlled by the temperature of the indoor heat exchanger to prevent the con-
densing pressure from increasing excessively.
When the temperature of indoor heat exchanger becomes too high, the high pressure protection works.
The indoor fan operates following the cold air prevention control. This mode continues until the temperature of indoor
heat exchanger falls.
3. Defrosting
Defrosting starts when the temperature of outdoor heat exchanger becomes too low.
The compressor stops once, the indoor/outdoor fans stop, the 4-way valve reverses, and the compressor re-starts.
This mode continues until the temperature of outdoor heat exchanger rises or the fixed time passes.
(3) Positioning
To confirm the standard position, the vane moves until it touches the vane stopper. Then the vane is set to the selected
angle.
Confirmation of standard position is performed in the following cases:
(a) When the operation starts or finishes (including timer operation).
(b) When the test run starts.
(c) When standby mode (only during multi system operation) starts or finishes.
8-4. AUTO VANE OPERATION
1. Horizontal vane
(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 (approximately 12 V) transmitted from indoor microprocessor.
(2) The horizontal vane angle and mode change as follows by pressing VANE CONTROL button.
AUTO 1 2 3 4 5 SWING
OBH746B

14
Horizontal
position
5
(4) VANE AUTO ( ) mode
In VANE AUTO mode, the microprocessor automatically determines the vane angle to make the optimum room tempera-
ture distribution.
(5) STOP (operation OFF) and ON TIMER standby
In the following cases, the horizontal vane returns to the closed position.
(a) When STOP/OPERATE (OFF/ON) button is pressed (POWER OFF).
(b) When the operation is stopped by the emergency operation.
(c) When ON TIMER is ON standby.
(6) Dew prevention
During COOL or DRY operation with the vane angle at Angle 4 or 5 when the compressor cumulative operation time
exceeds 0.5 - 1 hour, the vane angle automatically changes to Angle 2 for dew prevention.
(7) SWING ( ) mode
By selecting SWING mode with VANE CONTROL button, the horizontal vane swings vertically.
(8) Cold air prevention in HEAT operation.
The horizontal vane position is set to Upward.
NOTE: When 2 or more indoor units are operated with multi outdoor unit, even if any indoor unit turns thermostat off,
this control does not work in the indoor unit.
(9) ECONO COOL ( ) operation (ECONOmical operation)
When ECONO COOL button is pressed in COOL mode, set temperature is automatically set 4°F (2°C) higher.
Also the horizontal vane swings in various cycle.
SWING operation makes you feel cooler than set temperature. So, even though the set temperature is higher, the air
conditioner can keep comfort. As a result, energy can be saved.
ECONO COOL operation is cancelled when ECONO COOL button is pressed once again or VANE CONTROL button is
pressed or change to other operation mode.
8-5. TIMER OPERATION (ON/OFF TIMER)
1. How to set the timer
(1) Press STOP/OPERATE (OFF/ON) button to start the air conditioner.
(2) Select the timer mode by pressing the button during operation.
Each time this button is pressed, the timer mode is changed in sequence:
(OFF TIMER) ĺ(ON TIMER) ĺTIMER RELEASE
(3) Set the time of the timer using the button.
Each time this button is pressed, the set time increase or decrease by 1 hour to 12 hours.
2. To release the timer
Press the button until (OFF TIMER) and (ON TIMER) are not displayed.
NOTE :
• The OFF TIMER and the ON TIMER cannot be set at the same time.
• The displayed time is the time remaining and will decrease in 1-hour increments as time passes.
Horizontal
position
In COOL and DRY operation
Vane angle is fixed to Horizontal position.
In HEAT operation
Vane angle is fixed to Angle 4.
MSZ-HM18/24NA
MSZ-HM09/12/15NA
In COOL and DRY operation
Vane angle is fixed to Horizontal position. In HEAT operation Vane angle is fixed to Angle 5.
OBH746B

15
EMERGENCY OPERATION switch
8-6. EMERGENCY/TEST OPERATION
In the case of test run operation or emergency operation, use EMERGENCY OPERATION switch on the right side of the
indoor unit. Emergency operation is available when the remote controller is missing or has failed, or when the batteries in
the remote controller are running down. The unit will start and OPERATION INDICATOR lamp will light up.
The first 30 minutes of operation is the test run operation. This operation is for servicing. The indoor fan runs at High
speed and the temperature control does not work.
After 30 minutes of test run operation, the system shifts to EMERGENCY COOL/HEAT MODE with a set temperature of
75°F (24°C). The fan speed shifts to Med.
The coil frost prevention works even in the test run or the emergency operation.
In the test run or emergency operation, the horizontal vane operates in VANE AUTO ( ) mode.
Emergency operation continues until EMERGENCY OPERATION switch is pressed once or twice or the unit receives any
signal from the remote controller. In the latter case, normal operation will start.
NOTE: Do not press EMERGENCY OPERATION switch during normal operation.
Operation mode COOL HEAT
Set temperature 75°F (24°C) 75°F (24°C)
Fan speed Med. Med.
Horizontal vane Auto Auto
The operation mode is indicated by the
Operation Indicator lamp as follows:
Operation Indicator lamp
EMERGENCY COOL
Ļ
EMERGENCY HEAT
Ļ
STOP
Lighted
Not lighted
8-7. 3-MINUTE TIME DELAY OPERATION
When the system turns OFF, compressor will not restart for 3 minutes as 3-minute time delay function operates to protect
compressor from overload.
8-8. Changing temperature indication (°F/°C)
• The preset unit is °F.
• °F ĺ°C: Press RESET button while the TEMPERATURE buttons are pressed.
• °C ĺ°F: Press RESET button while the TEMPERATURE buttons are pressed.
Press RESET button gently
using a thin instrument.
OBH746B

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9-1. CAUTIONS ON TROUBLESHOOTING
1. Before troubleshooting, check the following
1) Check the power supply voltage.
2) Check the indoor/outdoor connecting wire for miswiring.
2. Take care of the following during servicing
1) Before servicing the air conditioner, be sure to turn OFF the unit first with the remote controller, and then after confirm-
ing 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 P.C. board.
3) When removing the 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 connector housing. 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 OPERATION INDICATOR lamp is flashing ON and OFF before starting ser-
vice work.
2) Before servicing check that the connector and terminal are connected properly.
3) When the P.C. board seems to be defective, check the copper foil pattern for disconnection and the components for
bursting and discoloration.
4) When troubleshooting, refer to 9-2, 9-3 and 9-4.
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.
Lead wiring Connector housing
<Incorrect> <Correct>
9TROUBLESHOOTING
MSZ-HM09NA MSZ-HM12NA MSZ-HM15NA MSZ-HM18NA MSZ-HM24NA
Insert the negative pole of the
batteries first. Check if the polarity
of the batteries is correct.
NOTE: 1. If RESET button is not pressed, the remote controller may not operate correctly.
2. This remote controller has a circuit to automatically reset the microcomputer when batteries are replaced.
This function is equipped to prevent the microcomputer from malfunctioning due to the voltage drop caused by the
battery replacement.
3. Do not use the leaking batteries.
Press RESET button with a thin instrument, and
then use the remote controller.
Remove the back lid and insert batteries.
Then reattach the back lid.
OBH746B

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9-2. FAILURE MODE RECALL FUNCTION
Outline of the function
This air conditioner can memorize the abnormal condition which has occurred once.
Even though LED indication listed on the troubleshooting check table (9-4.) disappears, the memorized failure details can
be recalled.
1. Flow chart of failure mode recall function
for the indoor/outdoor unit
Does upper lamp of OPERATION INDICATOR
lamp on the indoor unit blink at the interval of 0.5
seconds?
Blinks: Either indoor or outdoor unit is abnormal.
Beep is emitted at the same timing as the
blinking of upper lamp of OPERATION
INDICATOR lamp. 2
Indoor unit is normal.
But the outdoor unit might be abnormal because there are some abnor-
malities that cannot be recalled with this way.
Check if outdoor unit is abnormal according to the detailed outdoor unit
failure mode recall function.
No
Yes
The cause of abnormality cannot be found because the abnormality does not recur.
Setting up the failure mode recall function
Turn ON the power supply.
<Preparation of the remote controller>
While pressing both OPERATION SELECT button and TOO COOL button on the
remote controller at the same time, press RESET button.
First, release RESET button.
Hold down the other 2 buttons for another 3 seconds. Make sure that the indicators on
the LCD screen shown in the right ¿gure are all displayed.
Then release the buttons.
Press STOP/OPERATE (OFF/ON) button of the remote controller (the set temperature is
displayed) with the remote controller headed towards the indoor unit. 1
Judgment of indoor/outdoor abnormality
Before blinking, does upper lamp of
OPERATION INDICATOR lamp stay ON for 3
seconds?
When it stays ON for 3 seconds (without beep):
The outdoor unit is abnormal.
The indoor unit is abnormal.
Check the blinking pattern, and identify the abnormal point by referring to the
indoor unit failure mode table. (Refer to 9-2.2)
Make sure to check at least 2 consecutive blinking cycles. 2
Releasing the failure mode recall function
Release the failure mode recall function by the following procedures.
Turn OFF the power supply and turn it ON again.
Press RESET button of the remote controller.
The outdoor unit is abnormal.
Check the blinking pattern, and identify the abnormal point by referring
to the outdoor unit failure mode table. (Refer to outdoor unit service
manual.)
Make sure to check at least 2 consecutive blinking cycles. 3
Repair the failure parts.
Deleting the memorized abnormal condition
After repairing the unit, recall the failure mode again according to "Setting up the failure mode recall
function" mentioned above.
Press STOP/OPERATE (OFF/ON) button of the remote controller (the set temperature is displayed)
with the remote controller headed towards the indoor unit.
Press EMERGENCY OPERATION switch so that the memorized abnormal condition is deleted.
Release the failure mode recall function according to "Releasing the failure mode recall function"
mentioned above.
Operational procedure
Yes
(Blinks)
No
(OFF)
NOTE: 1. Make sure to release the failure mode recall function after it is set up, otherwise the unit cannot operate properly.
2. If the abnormal condition is not deleted from the memory, the last abnormal condition is kept memorized.
2. Blinking pattern when the indoor unit is abnormal:
3.Blinking pattern when the outdoor unit is abnormal:
ON
OFF Beeps
Repeated cycle Repeated cycle
ON
OFF No beep Beeps
Repeated cycle
2.5-second OFF Blinking at 0.5-
second interval
2.5-second OFF 3-second ON Blinking at 0.5-
second interval
Beeps Repeated cycle
2.5-second OFF Blinking at 0.5-
second interval
No beep Beeps
Repeated cycle
2.5-second OFF 3-second ON Blinking at 0.5-
second interval
Repeated cycle
Beeps
1 Regardless of normal or abnormal condition,
a short beep is emitted once the signal is re-
ceived.
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18
2. Indoor unit failure mode table
Upper lamp of OP-
ERATION INDICA-
TOR lamp Abnormal point
(Failure mode) Condition Remedy
Not lighted Normal — —
1-time Àash every
0.5-second Room temperature thermistor The room temperature thermistor short or
open circuit is detected every 8 seconds dur-
ing operation. Refer to the characteristics of the room temperature
thermistor (9-7.).
2-time Àash
2.5-second OFF Indoor coil
thermistor The indoor coil thermistor short or open circuit
is detected every 8 seconds during operation. Refer to the characteristics of the main indoor coil ther- mistor, the sub indoor coil thermistor (9-7.).
3-time Àash
2.5-second OFF Serial signal The serial signal from outdoor unit is not re-
ceived for a maximum of 6 minutes. Refer to 9-6. "How to check miswiring and serial
signal error".
11-time Àash
2.5-second OFF Indoor fan motor The rotational frequency feedback signal is
not emitted for 12 seconds after the indoor fan
motor is operated. Refer to 9-6. "Check of indoor fan motor".
12-time Àash
2.5-second OFF Indoor control system It cannot properly read data in the nonvolatile
memory of the indoor electronic control P.C.
board. Replace the indoor electronic control P.C. board.
NOTE: Blinking patterns of this mode differ from the ones of TROUBLESHOOTING CHECK TABLE (9-4.).
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19
9-3. INSTRUCTION OF TROUBLESHOOTING
Indoor unit oper-
ates.
Outdoor unit
does not operate.
If blinking of OPERATION INDI-
CATOR lamp cannot be checked,
it can be checked with failure
mode recall function.
Indoor unit operates.
Outdoor unit does
not operate normally.
Indoor unit does
not receive the
signal from re-
mote controller.
OPERATION INDICATOR
lamp on the indoor unit is
Àashing ON and OFF.
Outdoor unit
operates only
in Test Run
operation.
Outdoor unit
does not
operate even
in Test Run
operation.
Unit does not
operate nor-
mal operation
in COOL or
HEAT mode.
Indoor unit
operates, when
EMERGENCY
OPERATION
switch is pressed.
Indoor unit does
not operate, when
EMERGENCY
OPERATION
switch is pressed.
Check room
temperature
thermistor.
Refer to 9-7.
"Test point
diagram and
voltage".
Refer to "How
to check
inverter/com-
pressor".
Refer to
"Check of R.V.
coil".
Refer to 9-6.
"Check of remote
controller and
indoor elec-
tronic control P.C.
board".
1. Check indoor/out-
door connecting wire.
(Check if the power is
supplied to the indoor
unit.)
2. Refer to 9-6. "Check
of indoor P.C. board
and indoor fan motor".
Upper lamp
Flash ON
and OFF at
0.5-second
intervals
Cause:
Indoor/Outdoor
unit
• Miswiring or
trouble of se-
rial signal.
Upper lamp
2-time Àash
Cause:
Indoor unit
• Trouble
of room
temperature
/ indoor coil
thermistor.
Upper lamp
3-time Àash
Cause:
Indoor unit
• Trouble of
indoor fan
motor.
Upper lamp
4-time Àash
Cause:
Indoor unit
• Trouble
of indoor
unit control
system.
Upper lamp
5-time Àash
Cause:
Outdoor unit
• Outdoor
power sys-
tem abnor-
mality.
Upper lamp
6-time Àash
Cause:
Outdoor unit
• Trouble of
thermistor in
outdoor unit.
Upper lamp
7-time Àash
Cause:
Outdoor unit
• Trouble of
outdoor con-
trol system.
Upper lamp
14-time Àash
or more
Cause:
Outdoor unit
• Other ab-
normality
Start
Refer to
9-6. "How
to check mis-
wiring and
serial signal
error".
Check room
temperature
thermistor
and indoor
coil thermis-
tor. Refer
to 9-7."Test
point diagram
and voltage".
Refer to
9-6. "Check
of indoor fan
motor".
Replace the
indoor elec-
tronic control
P.C. board.
Refer to
"How to
check
inverter/com-
pressor".
Refer to
"Check of
outdoor ther-
mistors".
Replace the
inverter P.C.
board or
the outdoor
electronic
control P.C.
board.
Check "Flow
chart of the
detailed
outdoor unit
failure mode
recall func-
tion."
"Test Run operation" means the
operation within 30 minutes af-
ter EMERGENCY OPERATION
switch is pressed.
Refer to outdoor unit service manual.
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20
9-4. TROUBLESHOOTING CHECK TABLE
Before taking measures, make sure that the symptom reappears for accurate troubleshooting.
When the indoor unit has started operation and detected an abnormality of the following condition (the first detection after the
power ON), the indoor fan motor turns OFF and OPERATION INDICATOR lamp flashes.
OPERATION INDICATOR Lighted
Blinking
Not lighted
No. Abnormal
point Operation indicator lamp Symptom Condition Remedy
1Miswiring or serial
signal
Upper lamp Àashes.
0.5-second ON
0.5-second OFF
Indoor unit and
outdoor unit do
not operate.
The serial signal from the outdoor unit is not
received for 6 minutes. • Refer to 9-6. "How to check
miswiring and serial signal er-
ror".
2
Indoor coil
thermistor Upper lamp Àashes.
2-time Àash
2.5-second OFF
The indoor coil or the room temperature ther-
mistor is short or open circuit.
• Refer to the characteristics of
indoor coil thermistor, and the
room temperature thermistor
(9-7.).
Room tem-
perature
thermistor
3Indoor fan
motor
Upper lamp Àashes.
3-time Àash
2.5-second OFF
The rotational frequency feedback signal is
not emitted during the indoor fan operation. • Refer to 9-6. "Check of in-
door fan motor".
4Indoor con-
trol system
Upper lamp Àashes.
4-time Àash
2.5-second OFF
It cannot properly read data in the nonvolatile
memory of the indoor electronic control P.C.
board. • Replace the indoor electronic
control P.C. board.
5Outdoor power sys-
tem
Upper lamp Àashes.
5-time Àash
2.5-second OFF
It consecutively occurs 3 times that the com-
pressor stops for overcurrent protection or
start-up failure protection within 1 minute after
start-up.
• Refer to "How to check of in-
verter/compressor".
Refer to outdoor unit service
manual
• Check the stop valve.
6Outdoor
thermistors
Upper lamp Àashes.
6-time Àash
2.5-second OFF
The outdoor thermistors short or open circuit
during the compressor operation.
• Refer to "Check of outdoor
thermistor".
Refer to outdoor unit service
manual.
7Outdoor control sys-
tem
Upper lamp Àashes.
7-time Àash
2.5-second OFF
It cannot properly read data in the nonvolatile
memory of the inverter P.C. board or the out-
door electronic control P.C. board.
• Replace the inverter P.C. board
or the outdoor electronic control
P.C. board.
Refer to outdoor unit service
manual.
8Other ab-
normality
Upper lamp Àashes.
14-time Àash or more
2.5-second OFF
An abnormality other than above mentioned
is detected.
• Check the stop valve.
• Check the 4-way valve.
• Check the abnormality in detail
using the failure mode recall
function for outdoor unit.
9Outdoor control sys-
tem Upper lamp lights up. Outdoor unit
does not oper-
ate
It cannot properly read data in the nonvolatile
memory of the inverter P.C. board or the out-
door electronic control P.C. board.
• Check the blinking pattern of
the LED on the inverter P.C.
board or the outdoor electronic
control P.C. board.
OBH746B