Mitsubishi OBH483A Service Manual

SPLIT-TYPE AIR CONDITIONERS

INDOOR UNIT

SERVICE MANUAL

Models

Revision A:

• MLZ-KA25/35/50VA-

added.

Please void OBH483.

No. OBH483

REVISED EDITION-A

E2

have been

MLZ-KA25VA ­MLZ-KA25VA ­MLZ-KA35VA ­MLZ-KA35VA ­MLZ-KA50VA ­MLZ-KA50VA -

MLZ-KA25VA
MLZ-KA35VA
MLZ-KA50VA

E1

E2

E1

E2

E1

E2

Outdoor unit service manual
MXZ-A VA Series (OB377)
MXZ-B VA Series (OBH554)

CONTENTS

1. TECHNICAL CHANGES ··································· 2

2. PART NAMES AND FUNCTIONS ····················· 3

3. SPECIFICATION ················································ 4

4. NOISE CRITERIA CURVES ······························ 5

5. OUTLINES AND DIMENSIONS ························6

6. WIRING DIAGRAM ············································ 7

7. REFRIGERANT SYSTEM DIAGRAM ··············· 9

8. SERVICE FUNCTIONS ··································· 10

9. MICROPROCESSOR CONTROL ··················· 12

10. TROUBLESHOOTING ····································· 17

11. DISASSEMBLY INSTRUCTIONS ···················· 31

NOTE:

• RoHS compliant products have <G> mark on the spec name plate.

PARTS CATALOG (OBB483)

Revision A :

• MLZ-KA25/35/50VA-

E2

have been added.

1

MLZ-KA25VA-E1 MLZ-KA25VA­MLZ-KA35VA-E1 MLZ-KA35VA­MLZ-KA50VA-E1 MLZ-KA50VA-

1. Fan motor has been changed (RC0J30-KC RC0J30-KK).

2. Control of auto fan speed has been changed. (When indoor units are connected with a multi type outdoor
unit, and operated in heat mode.)
Air flow in auto fan speed is changed depending on air outlet temperature of indoor unit.

3. Electronic control P.C. board has been changed.

TECHNICAL CHANGES

E2

E2

E2

2

2

Vertical vane

Air outlet

Horizontal vane

Air filter
(Catechin air filter, option)

Air cleaning filter
(Anti-Allergy Enzyme
Filter, option)

Safety string

Intake grille

Remote control
receiving section

Display and operation section (When the intake grille is opened)

Operation indicator lamp

Emergency operation switch

Air inlet

PART NAMES AND FUNCTIONS

INDOOR UNIT

MLZ-KA25VA
MLZ-KA35VA
MLZ-KA50VA

ACCESSORIES

Alkaline battery (AAA) for remote controller
Drain hose (with insulation)
Special washer (with cushion, 4pcs)
Installation template
Fixing screw for M5 х 30
Band
Fixing screw for 4 х 16
Remote controller
Remote controller holder
Fixing screw for

MLZ-KA25VA
MLZ-KA35VA

MLZ-KA50VA

2
1
8
1
4
1
2
1
1
2

3

3

SPECIFICATION

Indoor model

Function

Power supply

Capacity

Air flow (High/Med./Low)
Running current 1
Power input 1
Auxiliary heater
Power factor 1

Electrical

data

Fan motor current 1

Fan motor

Model

Dimensions W x H x D
Weight
Air direction
Sound level (High/Med./Low)
Fan speed (High/Med./Low)

Special

remarks

Fan speed regulator
Remote controller model

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
Outdoor Dry-bulb temperature 7°C Wet-bulb temperature 6°C
Refrigerant piping length (one way): 5m

1 Measured under rated operating frequency.

3

m

/h

A

W

A(kW)

%

A

mm

kg

dB(A)

rpm

Cooling

Single phase

230V,50Hz

528/ 480/ 432

E1

RC0J30-KC

E2 E2

RC0J30-KK

1,102

35/ 32/ 29

1,120/1,030/950

Heating

552/ 492/ 420

0.3
40
—
58

0.3

175

x

KM07E

360

x

15

5

36/ 32/ 28

1,160/ 1,060/ 930

3

MLZ-KA35VAMLZ-KA25VA MLZ-KA50VA

Cooling

Single phase

230V,50Hz

564/ 504/ 438

E1 E1

RC0J30-KC
RC0J30-KK

1,102

37/ 34/ 31

1,180/ 1,080/ 960

Heating

594/ 528/ 462

0.3
40
—
58

0.3

175

x

KM07E

360

x

15

5

38/ 35/ 31

1,230/ 1,120/ 1,000

3

Cooling

Single phase

230V,50Hz

684/ 588/ 498

RC0J30-KC

E2

RC0J30-KK

1,102

43/ 38/ 34

1,380/1,220/1,070

708/ 618/ 528

0.3
40
—
58

0.3

175

x

x

15

5

43/ 39/ 34

1,420/ 1,270/ 1,120

3

KM07E

Heating

360

Specifications and rating conditions of main electric parts

Item

Fuse

Horizontal vane motor

Vertical vane motor

Varistor

DRAIN PUMP

FLOAT SENSOR

Model

(F11)

(MV1)

(MV2)

(NR11)

(DP)

(FS)

MLZ-KA25VA MLZ-KA35VA MLZ-KA50VA

T3.15AL 250V

12V 300Ω

12V 300Ω

ERZV14D471

230V 6.4W

DC 12V

4

4

NOISE CRITERIA CURVES

MLZ-KA25VA

FAN SPEED

High

FUNCTION

COOLING

HEATING

SPL(dB(A))

35

36

Test conditions,
Cooling: Dry-bulb temperature 27ºC Wet-bulb temperature 19ºC

Heating: Dry-bulb temperature 20ºC

90

80

70

60

50

40

30

APPROXIMATE

20

THRESHOLD OF
HEARING FOR
CONTINUOUS

OCTAVE BAND SOUND PRESSURE LEVEL, dB re 0.0002 MICRO BAR

NOISE

10

63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCIES, Hz

LINE

MLZ-KA35VA

FAN SPEED

High

FUNCTION

COOLING

HEATING

Test conditions,
Cooling: Dry-bulb temperature 27ºC Wet-bulb temperature 19ºC

Heating: Dry-bulb temperature 20ºC

90

80

NC-70

70

60

NC-60

50

NC-50

40

NC-40

30

NC-30

APPROXIMATE

20

THRESHOLD OF

NC-20

OCTAVE BAND SOUND PRESSURE LEVEL, dB re 0.0002 MICRO BAR

HEARING FOR
CONTINUOUS
NOISE

10

63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCIES, Hz

SPL(dB(A))

LINE

37

38

NC-70

NC-60

NC-50

NC-40

NC-30

NC-20

MLZ-KA50VA

FAN SPEED

High

FUNCTION

COOLING

HEATING

SPL(dB(A))

43

43

Test conditions,
Cooling: Dry-bulb temperature 27ºC Wet-bulb temperature 19ºC

Heating: Dry-bulb temperature 20ºC

90

80

70

60

50

40

30

APPROXIMATE

20

THRESHOLD OF
HEARING FOR
CONTINUOUS

OCTAVE BAND SOUND PRESSURE LEVEL, dB re 0.0002 MICRO BAR

NOISE

10

63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCIES, Hz

LINE

NC-70

NC-60

NC-50

NC-40

NC-30

NC-20

INDOOR UNIT

1.4m

MICROPHONE

CEILING

GRILLE

5

5

OUTLINES AND DIMENSIONS

MLZ-KA25VA MLZ-KA35VA MLZ-KA50VA

INDOOR UNIT

(Top)

180

(51.6)

49.7

20

(Front)

Grille (MLP-440W)

Receiving section

172.4

166.5

81.8

0

166.5
173

R6

(Top)

38

15

13.5

Electrical box

Air outlet

Electrical box

466.5

Center of ceiling opening, suspension bolt pitch
and grille are located in one position.

Drain hose
connecting part

1051 Suspension bolt pitch

1102

960

Outlet opening area

2

0.04m

1200

CL

0

10

Center of ceiling opening,
suspension bolt pitch and grille
are located in one position.

Drain hose

Drain pan

15

2

2

26

58

Pipe
cover

230

20

78

Pipe cover

48

No gaps between

Φ58

the ceiling surface and grille

466.5

26

(Right side)

Drain hose
connecting
part (drain pipe
VP20)

Drain pipe
VP20

R6

CL

414

Hole position for the
installation of grille

How to connect drain pipe on indoor
unit by lifting drain hose.
Drain hose can be used by cutting it.

Wireless
remote controller

58 18

308

116

25

158

Suspension bolt pitch

Gas pipe
MLZ-KA25/35: Φ9.52
MLZ-KA50 : Φ12.7
(Flared)

Liquid pipe

110

Φ6.35
(Flared)

112

Ceiling
surface

Φ6.35

Φ9.52 (MLZ-KA25/35)
Φ12.7 (MLZ-KA50)

110

34

Refrigerant

Pipe

360

244

170

60

Display and
receiving section

Liquid

Gas

Length of drain hose 540

Drain pipe

VP20

NOTE: Drain hose can be used by cutting it.

Drain pipe VP20

Unit : mm

175

31

308 Suspension bolt pitch

384 Ceiling opening

414 Outer side of grille

38

15

54.5

20

(Front)

175

180 or more

Ceiling surface

Air outlet

Outlet

1051 Suspension bolt pitch

1160 Ceiling opening

1200 Outer side of grille

Grille

54.5

20

Suspension bolt M10

Ceiling surface

6

500mm or less

Decline 1/100

Drain hose

6

WIRING DIAGRAM

INDOOR UNIT

MLZ-KA25VA­MLZ-KA35VA-

E1

E1

MLZ-KA25VA­MLZ-KA35VA-

E2

E2

7

MLZ-KA50VA-

E1

MLZ-KA50VA-

E2

8

7

REFRIGERANT SYSTEM DIAGRAM

INDOOR UNIT

MLZ-KA25VA
MLZ-KA35VA

MLZ-KA50VA

Unit : mm

Indoor
heat
exchanger

Indoor coil
thermistor
RT13 (sub)

Room temperature
thermistor
RT11

Indoor coil
thermistor
RT12 (main)

Refrigerant pipe Φ9.52
(with heat insulator)

Flared connection

Flared connection

Refrigerant pipe Φ6.35
(with heat insulator)

Indoor
heat
exchanger

Indoor coil
thermistor
RT13 (sub)

Room temperature
thermistor
RT11

Indoor coil
thermistor
RT12,RT14,
RT15 (main)

Refrigerant pipe Φ12.7
(with heat insulator)

Flared connection

Flared connection

Refrigerant pipe Φ6.35
(with heat insulator)

Refrigerant flow in cooling
Refrigerant flow in heating

9

8

SERVICE FUNCTIONS

MLZ-KA25VA
MLZ-KA35VA
MLZ-KA50VA

8-1. 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. (Refer to 10-7.)
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.)

8-2. P.C. BOARD MODIFICATION FOR INDIVIDUAL OPERATION

A maximum of 4 indoor units with wireless remote controllers can be used in a room.
In this case, to operate each indoor unit individually by each remote controller, both the P.C. boards of remote controller

and the electronic control 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:

NOTE: For modification, take out the bat-

teries and press the OPERATE/
STOP (ON/OFF) button 2 or 3
times at first.

After modification, put back the

batteries then press the RESET
button.

J1

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.

J2

Table 1

1 unit operation

No. 1 unit

No. 2 unit

No. 3 unit

No. 4 unit

How to modify the electronic control P.C. board

Turn OFF the power supply before modification. Cut off “JR05” and “JR06” on the electronic control P.C. board according
to the number of indoor unit as shown in Table 2. (Refer to 10-7.)

No modification

–

–

–

2 units operation

Same as at left

Solder J1

–

–

Table 2

No. 1 unit

No. 2 unit

No. 3 unit

No. 4 unit

JR05

No modification

Cut off JR05

No modification

Cut off JR05

JR06

No modification

No modification

Cut off JR06

Cut off JR06

3 units operation

Same as at left

Same as at left

Solder J2

–

Fuse (F11)

VARISTOR (NR11)

R111

Indoor electronic
control P.C. Board

C111

4 units operation

Same as at left

Same as at left

Same as at left

Solder both J1 and J2

JR06

JR05

IC101

T11

CN151

CN211

NOTE: After modification, turn ON the power supply and with the remote controller headed towards the indoor unit, press the

OPERATE/STOP (ON/OFF) button. If one or two beeps is heard from the indoor unit, modification is completed
correctly.

10

8-3. 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. The “AUTO RESTART FUNCTION” sets to work the moment
power has restored after power failure. Then, the unit will restart automatically.

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 release “AUTO RESTART FUNCTION”

Turn off the main power for the unit.
Solder the Jumper wire to JR07 on the indoor electronic control P.C. board. (Refer to 10-7.)

F11

NR11

CN 111

CN112 CN113

IC101

CN106

NOTE:

• The operation settings are memorized when 10 seconds have passed after

JR07

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 tripping 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.

R111

C111

CN151

T11

CN211

8-4. P.C. BOARD MODIFICATION FOR CHANGING AIRFLOW VOLUME

Change dip switch SW3 setting according to the height of ceiling.

Dip switch SW3

Ceiling height

NOTE: When the ceiling is above 2.7 m, airflow volume may be insufficient even with the Dip switch (SW3)
set to "increase airflow.

Normal

2.4 m or below

Increase airflow volume

above 2.4 m and 2.7 m or below

How to change Dip switch (SW3) setting (Default setting is Normal)

1. Turn OFF the power supply for the air conditioner.

2. Remove electrical cover A and B.

3. Slide out electronic control P.C. board, and switch
up or down Dip switch (SW3).

4. Put electronic control P.C. board back to
the original position, and install electrical cover A and B.

NOTE:

To prevent damage of P.C. board due to static electricity,
make sure to perform static elimination before setting.

Electrical
cover B

11

Electrical
cover A

Electronic control P.C. board

Dip switch SW3

Normal

Increase
airflow volume

9

MICROPROCESSOR CONTROL

MLZ-KA25VA
MLZ-KA35VA
MLZ-KA50VA

WIRELESS REMOTE CONTROLLER

Signal transmitting section

Operation display section

OPERATE/STOP
(ON/OFF) button

Temperature buttons

Open the front lid.

FAN SPEED CONTROL button

OPERATION SELECT button

ECONO COOL button

RESET button

Indication of
remote controller
model is on back

r

WIDE VANE button

OFF-TIMER button

ON-TIMER button

TIME SET buttons
FORWARD button
BACKWARD button

CLOCK SET button

VANE CONTROL button

Once the operation mode is set, the same operation mode can be repeated by simply turning 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.

12

INDOOR UNIT DISPLAY SECTION

Operation Indicator lamp

The operation indicator at the left side of the indoor unit indicates the operation state.

Difference between target

Operation stateIndication

temperature and
room temperature

This shows that the air conditioner is
operating to reach the target temperature.
Please wait until the target temperature is obtained.

Approximate
2ºC or more

Lighted

Blinking

This shows that the room temperature is
approaching the target temperature.

This shows a state of standby for operation.
(For multi system air conditioner)

9-1. 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 OPERATION SELECT button.
(3) Press TEMPERATURE buttons (TOO WARM or TOO COOL button) to select the desired temperature.
The setting range is 16 ~ 31°C.

1. Coil frost prevention
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.

9-2. 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 OPERATION SELECT button.
(3) The set temperature is determined from the initial room temperature.

1. Coil frost prevention

Coil frost prevention is as same as COOL mode. (9-1.1.)

Approximate
2ºC or less

Not lighted

9-3. HEAT ( ) OPERATION

(1) Press OPERATE/STOP (ON/OFF) 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 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
temperature is low or when defrosting is being done, the indoor fan will stop or rotate in Very Low speed.

9-4. AUTO CHANGE OVER ··· AUTO MODE OPERATION

Once desired temperature is set, unit operation is switched automatically between COOL and HEAT operation.

Mode selection

(1) Initial mode
When unit starts the operation with AUTO operation from off;

• If the room temperature is higher than the set temperature, operation starts in COOL mode.

• If the room temperature is equal to or lower than the set temperature, operation starts in HEAT mode.

(2) Mode change
COOL mode changes to HEAT mode when about 15 minutes have passed with the room temperature 2 degrees
below the set temperature.
HEAT mode changes to COOL mode when about 15 minutes have passed with the room temperature 2 degrees
above the set temperature.

NOTE:

If two or more indoor units are operating in multi system, there might be a case that the indoor unit, which is operating
in

(AUTO), cannot change over to the other operating mode (COOL HEAT) and becomes a state of standby.

13

9-5. 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 12V) transmitted from indoor microprocessor.

(2) The horizontal vane angle and mode change as follows by pressing VANE CONTROL button.

12345

(3) Positioning
To confirm the standard position, the vane moves until it touches the vane stopper. Then the vane is set to the desired

angle.
Confirming of standard position is performed in the following cases:
(a) When the power supply turns on.
(b) When the operation starts or finishes (including timer operation).
(c) When the test run starts.
(d) When multi-standby starts or finishes.
(e) When the swing operation finishes.

(4) VANE AUTO ( ) mode

In VANE AUTO mode, the microprocessor automatically determines the vane angle and operation to make the optimum

room-temperature distribution.

(1) In COOL and DRY operation

(2) In HEAT operation

(5) STOP (operation OFF) and ON-TIMER standby

In the following cases, the horizontal vane returns to the closed position.

(a) When OPERATE/STOP (ON/OFF) button is pressed (POWER OFF).

(b) When the operation is stopped by the emergency operation.

(c) When ON-TIMER is ON standby.

(6) SWING MODE (

By selecting SWING mode with VANE CONTROL button, the horizontal vane swings vertically. The remote controller

displays “”. SWING mode is cancelled when VANE CONTROL button is pressed once again.

(7) Cold air prevention in HEAT operation

The horizontal vane position is set to Upward.

(8) ECONO COOL ( ) operation (ECONOmical operation)

When ECONO COOL button is pressed in COOL mode, set temperature is automatically set 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.

)

Vane angle is fixed to Angle 1.

Vane angle is fixed to Angle 5.

1

5

14

2. Vertical vane

(1) Press WIDE VANE button to change horizontal airflow direction.

•The vertical vane moves for about 30 seconds.
(After 30 seconds, the vertical vane moves to its original position. In this case, press WIDE VANE button again.)
(2) Press WIDE VANE button again to set horizontal airflow direction.

•The vertical vane stops and the airflow direction is set.
(3) Positioning
To confirm the standard position, the vane moves until it touches the vane stopper. Then the vane set to the desired

angle.

Confirming of standard position is performed in the following cases:
(a) When OPERATE/STOP (ON/OFF) button is pressed (POWER ON).
(b) When SWING is started.

9-6. Drain pump/ float sensor control

1. Drain pump

Operating condition:

1. During COOL, DRY, or emergency COOL operation

2. When float sensor detects water level above fixed point during:
(a) HEAT operation.
(b) emergency HEAT operation.
(c) standby when during multi system operation.
(d) standby when ON timer is set.
(e) operation STOP.

Drain pump operates in conditions 1 or 2.

Operation stop condition:
Condition other than 1 or 2 indicated above.

2. Float sensor

Float moves with the up and down of water surface inside the drain pan, and judges water level.
(Fixed point differs at raised and lowered water levels.)

Float sensor

Fixed point, when water level rises

Fixed point, when water level lowers

Water surface

9-7. TIMER OPERATION

1. How to set the time

(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

TIME MONITOR, so set the current time correctly with CLOCK SET button.

How to set the current time

(1)Press the CLOCK set button.
(2)Press the TIME SET buttons (

• Each time FORWARD button ( ) is pressed, the set time increases by 1minute, and each time BACKWARD button

(

) is pressed, the set time decreases by 1minute.

• Pressing those buttons longer increases/decreases the set time by 10 minutes.
Press the CLOCK set button.

and ) to set the current time.

15

ON timer setting

(1) Press ON-TIMER button (

) during operation.

(2) Set the time of the timer using TIME SET buttons ( and ) .

OFF timer setting

(1) Press OFF-TIMER button (

) during operation.

(2) Set the time of the timer using TIME SET buttons ( and ).
Each time FORWARD button ( ) is pressed, the set time increases by 10 minutes; each time BACKWARD button

( ) is pressed, the set time decreases by 10 minutes.

2. Cancel

To cancel ON timer, press ON-TIMER button (

).

To cancel OFF timer, press OFF-TIMER button ( ).
TIMER is cancelled and the display of set time disappears.

PROGRAM TIMER

• OFF timer and ON timer can be used in combination. The timer of the set time that is reached first will operate first.

• “

” and “ ” display show the order of OFF timer and ON timer operation.

(Example 1) The current time is 8:00 PM.

The unit turns OFF at 11:00 PM, and ON at 6:00 AM.

(Example 2) The current time is 11:00 AM.

The unit turns ON at 5:00 PM, and OFF at 9:00 PM.

NOTE: If the main power is turned off or a power failure occurs while AUTO START/STOP timer is active, the timer setting

is cancelled. As these models are equipped with an auto restart function, the air conditioner starts operating with
timercancelled when power is restored.

9-8. EMERGENCY/TEST OPERATION

In case of test run operation or emergency operation, use EMERGENCY OPERATION switch on the front of the indoor
unit. Emergency operation is available when the remote controller is missing, has failed or the batteries of the remote
controller run down. The unit will start and 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 speed and the system is in continuous operation (The thermostat in ON).
After 30 minutes of test run operation, the system shifts to EMERGENCY COOL/HEAT MODE with a set temperature of
24°C. The fan speed shifts to Med.
The coil frost prevention works even in emergency operation, and defrosting too.
In the test run or emergency operation, the horizontal vane operates in VANE AUTO (
Emergency operation continues until EMERGENCY OPERATION switch is pressed once or twice or the unit receives any
signal from the remote controller. In case of latter, normal operation will start.

NOTE: Do not press EMERGENCY OPERATION switch during normal operation.

Operation mode COOL HEAT

Operation indicator lamp

Set temperature 24ºC 24ºC
Fan speed Medium Medium

Horizontal vane Auto Auto
EMERGENCY
OPERATION switch

The operation mode is indicated by the Operation
indicator lamp on the indoor unit as following

Operation Indicator lamp

Press once <COOL>

Press again <HEAT>

) mode.

Lighted
Not lighted

Press once again <STOP>

16

10

of the batteries is correct

TROUBLESHOOTING

MLZ-KA25VA MLZ-KA35VA MLZ-KA50VA

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 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

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.

Lead wiring

3. Troubleshooting procedure

1) First, check if the OPERATION INDICATOR lamp on the indoor unit is flashing ON and OFF to indicate an abnormality.
To make sure, check how many times the abnormality indication is flashing ON and OFF before starting service work.

2) Before servicing check that the connector and terminal are connected properly.

3) 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.

4) Refer to 10-2, 10-3 and 10-4.

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.

Remove the front lid and insert batteries.

Then reattach the front lid.

Insert the negative pole of the
batteries first. Check if the polarity

.

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.

Housing point

Press RESET button with tip end of ball point pen

or the like, and then use the remote controller.

RESET button

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 will not 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.
Operation indicator lamp flashes as shown in the figure below.

•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 cannot
operate and indicate as shown in the figure below. In this case, please set all the indoor units to the same operation mode.

OPERATION INDICATOR

•When indoor units start operation while the defrosting of outdoor unit is being done, it takes a few minutes (maximum
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

Not lighted

17

10-2. FAILURE MODE RECALL FUNCTION

Outline of the function
This air conditioner can memorize the abnormal condition which has occurred once.
Even though OPERATION INDICATOR lamp indication listed on the troubleshooting check table (10-4.) disappears, the
memorized failure details can be recalled.
This mode is very useful when the unit needs to be repaired for the abnormality which does not recur.

1. Flow chart of failure mode recall function for the indoor/outdoor unit

Operational procedure

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.
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.
And release the other two buttons after all LCD except the set
temperature in operation display section of the remote controller is
displayed after 3 seconds.

1. Regardless of normal or abnormal, a short

Press OPERATE/STOP (ON/OFF) button of the remote controller (the set temperature
is displayed) with the remote controller headed towards the indoor unit. 1

beep is emitted once as the signal is received.

Does the left 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 are emitted at the same timing
as the blinking of the left lamp of
OPERATION INDICATOR lamp. 2

Judgment of indoor/outdoor abnormality

Before blinking, does the left lamp of OPERATION
INDICATOR lamp stay ON for 3 seconds?
Stays ON for 3 seconds (without beep):
The outdoor unit is abnormal.

The indoor unit is abnormal.
Check the blinking pattern, and confirm the
abnormal point with the indoor unit failure mode table (10-2. 3.).
Make sure to check at least two 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.

Repair the defective parts.

Deleting the memorized
abnormal condition

After repairing the unit, recall the failure mode again according to "Setting up the failure
mode recall function".
Press OPERATE/STOP (ON/OFF) button of the remote controller (the set temperature is
displayed) with the remote controller headed towards the indoor unit. 1
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".

Yes

(Blinks)

No

No

(OFF)

Yes

Indoor unit is normal.
But the outdoor unit might be abnormal because there are some
abnormalities that are not memorized in the indoor unit.
Confirm if outdoor unit is abnormal according to the flow chart of the
detailed outdoor unit failure mode recall function.

The outdoor unit is abnormal.
Check the blinking pattern, and confirm the abnormal point with the
outdoor unit failure mode table (Refer to outdoor unit service manual).
Make sure to check at least two consecutive blinking cycles. 3

As for outdoor unit, refer to outdoor unit service manual.

Note1.Make sure to release the failure mode recall function once 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:

Blinking at 0.5-

2.5-second OFF

ON

OFF

3.Blinking pattern when the outdoor unit is abnormal:

2.5-second OFF 3-second ON

ON

OFF

second interval

Beeps

Repeated cycle Repeated cycle

No beep Beeps

Repeated cycle

2.5-second OFF

Blinking at 0.5­second interval

Blinking at 0.5­second interval

Beeps

2.5-second OFF 3-second ON

Beeps

Repeated cycle

No beep Beeps

Repeated cycle

18

Blinking at 0.5­second interval

Repeated cycle

2. Flow chart of the detailed outdoor unit failure mode recall function

Operational procedure

The outdoor unit might be abnormal.
Confirm if outdoor unit is abnormal according to the following procedures.

Confirm that the remote controller is in the failure mode recall
function.

With the remote controller headed towards the indoor unit, press TOO COOL or TOO
WARM button to adjust the set temperature to 25ºC. 1

1. Regardless of normal or abnormal, 2 short
beeps are emitted as the signal is received.

Does OPERATION INDICATOR lamp on the indoor
unit blink at the interval of 0.5 seconds?
Blinks: The outdoor unit is abnormal.
Beeps are emitted at the same timing as the
blinking of OPERATION INDICATOR lamp. 2

The outdoor unit is abnormal.
Check the blinking pattern, and confirm the abnormal point with the
outdoor unit failure mode table (Refer to outdoor unit service manual).
Make sure to check at least two 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.

Repair the defective parts.

Deleting the memorized abnormal condition

After repairing the unit, recall the failure mode again according to
"Setting up the failure mode recall function".
Press OPERATE/STOP (ON/OFF) 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".

Yes

(Blinks)

No

(OFF)

The outdoor unit is normal.

Release the failure mode recall function according
to the left mentioned procedure.

Note1. Make sure to release the failure mode recall function once 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 outdoor unit is abnormal:

2.5-second OFF 3-second ON

ON

OFF

No beep

Repeated cycle

Blinking at 0.5­second interval

Beeps

2.5-second OFF 3-second ON

No beep Beeps

Repeated cycle

19

Blinking at 0.5-

second interval

Repeated cycle

3. Indoor unit failure mode table
NOTE: Blinking patterns of this mode differs from the ones of Troubleshooting check table (10-4.).

Left lamp of

OPERATION

INDICATOR lamp

Not lighted –Normal –

1-time flash
every 0.5-second

2-time flash

2.5-second OFF

3-time flash

2.5-second OFF

5-time flash

2.5-second OFF

11-time flash

2.5-second OFF

12-time flash

2.5-second OFF

13-time flash

2.5-second OFF

Right lamp of

OPERATION

INDICATOR lamp

Not lighted

Not lighted

Not lighted

Not lighted

Not lighted

Not lighted

Not lighted

Not lighted

Abnormal point

(Failure mode)

Room temperature
thermistor

Indoor coil thermistor
(Main 1, 2 and sub)

[Main 2:MLZ-KA50VA]

Serial signal error

Drain pump

Float sensor

Indoor fan motor

Indoor control system

Indoor coil thermistor
(Main 3)

[MLZ-KA50VA]

When the room temperature thermistor
short or open circuit is detected every 8
seconds during operation.

When the indoor coil thermistor short or
open circuit is detected every 8 seconds
during operation.

When the serial signal from the outdoor unit is
not received for a maximum of 6 minutes.

• Float sensor is open.

• Float sensor detects abnormal water level.

When the rotational frequency feedback
signal is not emitted during 12-second the
indoor fan operation.

When it cannot be read properly data in the
nonvolatile memory of the indoor electronic
control P.C. board.

When the indoor coil thermistor short or
open circuit is detected every 8 seconds
during operation.

Check point

Countermeasure

Refer to the characteristics of the room
temperature thermistor (10-7.).

Refer to the characteristic of the main 1,2
indoor coil thermistor and the sub indoor
coil thermistor (10-7.).

Refer to 10-6. "How to check mis-wiring
and serial signal error".

• Check float sensor and drain pump.

• Check the connectors of float sensor
and drain pump.

• Refer to 10-6. "Check of float sensor".

Refer to 10-6. "Check of indoor
fan motor"

Replace the indoor electronic control
P.C. board.

Refer to the characteristic of the main
3 indoor coil thermistor (10-7.).

20

10-3. INSTRUCTION OF TROUBLESHOOTING

Start

Indoor unit
operates.
Outdoor unit
does not
operate.

Outdoor unit
operates only
in Test Run
operation.
1

Check room
temperature
thermistor.
Refer to 10-7.

"TEST POINT
DIAGRAM AND
VOLTAGE".

Left lamp
Flash on and off
at 0.5-second
intervals
Cause:
Indoor/
Outdoor unit

• Mis-wiring
or trouble
of serial signal

Outdoor unit
does not
operate
even in
Test Run
operation.
1

Refer to
"How to check
inverter/
compressor".

Left

lamp
2-time flash
Cause:
Indoor unit

• Trouble of
room temp­ erature/
indoor coil
thermistor

Indoor unit operates.
Outdoor unit does not
operate normally.

Unit does not
operate
normal
operation in
COOL or
HEAT mode.

Refer to
"Check of
R.V. coil".

Left

lamp
3-time flash
Cause:
Indoor unit

• Trouble of
indoor fan
motor

Left lamp
4-time flash
Cause:
Indoor unit

• Trouble of
indoor unit
control
system

Indoor unit
does not receive
the signal from
remote controller.

Indoor unit
operates, when
EMERGENCY
OPERATION
switch is pressed.

Refer to 10-6.
"Check of
remote controller
and receiver
P.C. board".

Left lamp
5-time flash
Cause:
Outdoor unit

• Outdoor
power
system
abnormality

OPERATION INDICATOR
lamp on the indoor unit is
flashing on and off.

Indoor unit
does not operate,
when
EMERGENCY
OPERATION
switch is pressed.

1. Check indoor/outdoor
connecting wire.
(Check if the power
is supplied to the
indoor unit.)

2. Refer to 10-6.
"Check of indoor
electronic control
P.C. board and indoor
fan motor".

Left lamp
6-time flash
Cause:
Outdoor unit

• Trouble of
thermistor
in outdoor
unit

If blinking of OPERATION
INDICATOR lamp cannot be
checked, it can be checked with
failure mode recall function.

1
"Test Run operation" means the
operation within 30 minutes after
EMERGENCY OPERATION switch
is pressed.

Refer to outdoor unit service manual.

Left lamp
7-time flash
Cause:
Outdoor unit

• Trouble of
outdoor
control
system

Left lamp
9-time flash
Cause:
Indoor unit

• Trouble of
float sensor
or drain
pump

Left lamp
14-time flash
Cause:
Outdoor unit

• Other
abnormality

• Check the
stop valve.

Refer to 10-6.
"How to
check
mis-wiring
and serial
signal error
(when
outdoor unit
does not work)".

Check room
temperature
thermistor
and indoor
coil thermis­tor.
Refer to 10-7.
"Test point
diagram and
voltage".

Refer to 10-6.
"Check of
indoor fan
motor".

Replace the
indoor
electronic
control
P.C. board.

Refer to
"How to check
the inverter/
compressor".

Refer to
"Check of
outdoor
thermistors".

21

Replace the
inverter P.C.
board or
the outdoor
electronic
control P.C.
board.

Refer to 10-6.
"Check of
float sensor".

Check the
drain pump.

Check
"Flow chart of
the detailed
outdoor unit
failure mode
recall function."

10-4. TROUBLESHOOTING CHECK TABLE

OPERATION INDICATOR

Lighted

Blinking

Not lighted

NOTE: Before taking measures, make sure that the symptom reappears for accurate troubleshooting.
Self check table

Abnormal

No.

point

Left lamp flashes.

Mis-Wiring
or serial

1

signal

0.5-second ON

0.5-second OFF

· Flashing of OPERATION INDICATOR lamp (left-hand side lamp) indicates
abnormalities.

SymptomOperation indicator lamp Check point

Indoor unit
and outdoor
unit do not
operate.

When the serial signal from the outdoor unit is
not received for a maximum of 6 minutes.

Countermeasure

• Refer to 10-6. "How to check
mis-wiring and serial signal
error".

Outdoor
control

2

system

Indoor coil
thermistor

3

Room
temperat­ure
thermistor

Indoor fan

4

motor

Indoor

5

control
system

Outdoor

6

power
system

Outdoor

7

thermistors

Outdoor

8

control
system

Drain

9

pump

Other

10

abnormality

Left lamp lights up.

Left lamp flashes.
2-time flash

2.5-second OFF

Left lamp flashes.
3-time flash

2.5-second OFF

Left lamp flashes.
4-time flash

2.5-second OFF

Left lamp flashes.
5-time flash

2.5-second OFF

Left lamp flashes.
6-time flash

2.5-second OFF

Left lamp flashes.
7-time flash

2.5-second OFF

Left lamp flashes.
9-time flash

2.5-second OFF

Left lamp flashes.
14-time flash

2.5-second OFF

Outdoor unit
does not
operate.

Indoor unit
and outdoor
unit do not
operate.

Indoor unit
and outdoor
unit do not
operate.

Indoor unit
and outdoor
unit do not
operate.

Indoor unit
and outdoor
unit do not
operate.

Indoor unit
and outdoor
unit do not
operate.

Indoor unit
and outdoor
unit do not
operate.

Indoor unit
and outdoor
unit do not
operate.

Indoor unit
and outdoor
unit do not
operate.

When it cannot properly read data in the
nonvolatile memory of the inverter P.C. board
or of the outdoor electronic control P.C. board.

When the indoor coil or the room temperature
thermistor is shorts or opens circuit.

When the rotational frequency feedback
signal is not emitted during the indoor fan
operation.

When it cannot properly read data in the
nonvolatile memory of the indoor electronic
control P.C. board.

The compressor stops 3 times consecutively
for over current protection or start-up failure
protection within 1 minute after start-up.

When the outdoor thermistors short or open
circuit during the compressor operation.

When it cannot properly read data in the
nonvolatile memory of the inverter P.C. board
or of the outdoor electronic control P.C. board.

• Float sensor is open.

• Float sensor detects abnormal water level.

An abnormality other than above mentioned is
detected.

• Check the blinking pattern of
the LED on the inverter P.C.
board or the outdoor
electronic control P.C. board.

• Refer to the characteristics of
indoor coil thermistor, and the
room temperature thermistor
on 10-7.

• Refer to 10-6. "Check of
indoor fan motor".

• Replace the indoor electronic
control P.C. board.

• Refer to "Check of inverter/
compressor".
Refer to outdoor unit service
manual.
Check the stop valve.

• Refer to "Check of outdoor
thermistor".
Refer to outdoor unit service
manual.

• Replace the inverter P.C.
board or the outdoor
electronic control P.C. board.
Refer to outdoor unit service
manual.

• Check float sensor
characteristics.

• Check drain pump.

• Check drain pipe.

• Check the connectors of float
sensor and drain pump.

• Refer to 10-6. "Check of float

sensor".

• Confirm the abnormality in
detail using the failure mode
recall function.
Refer to outdoor unit service
manual.

NOTE: When the indoor unit has started operation and the above failures are detected (the first detection after the power

ON), the indoor electronic control P.C. board turns OFF the indoor fan motor with OPERATION INDICATOR lamp
flashing.

22

OPERATION INDICATOR

No.

1

Abnormal

point

MXZ type

Operation
mode
setting

Lighted

Blinking

Not lighted

Right lamp flash

2.5-second OFF

· Flashing of OPERATION INDICATOR lamp (right-hand side lamp) indicates
abnormality.

· OPERATION INDICATOR lamp (left-hand side lamp) is lighted.

SymptomOperation indicator lamp Check point

Outdoor unit
operates but
indoor unit
does not
operate.

When the operation mode of the each indoor
unit is differently set to COOL (includes DRY)
and HEAT at the same time, the operation
mode of the indoor unit that has operated at
first has the priority.

Countermeasure

• Unify the operation mode.
Refer to outdoor unit
service manual.

NOTE: When the indoor unit has started operation and the above failures are detected (the first detection after the power

ON), the indoor electronic control P.C. board turns OFF the indoor fan motor with OPERATION INDICATOR lamp
flashing.

10-5. TROUBLE JUDGEMENT CRITERIA OF MAIN PARTS

MLZ-KA25VA MLZ-KA35VA MLZ-KA50VA

Part name FigureCheck method and criteria

Room temperature
thermistor (RT11)

Indoor coil thermistor
(RT12,RT14,RT15 (MAIN),
RT13 (SUB))

Measure the resistance with a tester. (Part temperature 10°C ~ 30°C)

Normal

8 kΩ ~ 20 kΩ

Indoor fan motor

Float sensor (FS)

Drain pump (DP)

Horizontal vane
motor (MV1)

Vertical vane
motor (MV2)

Check 10-6. .

Disconnect connector and check with a tester.
Check open or short according to the float position.

Float sensor Float sensor

Float
position

Float

Float

Normal Short Open

Measure the resistance between the terminals with a tester.
(Part temperature 10ºC ~ 30ºC)

Color of the lead wire

GRAY-GRAY

Normal

520Ω ~ 620Ω

Measure the resistance between the terminals with a tester.
(Part temperature 20ºC ~ 30ºC)

Color of the lead wire

BRN-other one

Normal

Each phase 380Ω

Measure the resistance between the terminals with a tester.
(Part temperature 20ºC ~ 30ºC)

Color of the lead wire

BRN-other one

Normal

Each phase 300Ω

RED

YLW
BRN

ROTOR

ORN

GRN

23

10-6. TROUBLESHOOTING FLOW

When the left lamp of OPERATION INDICATOR lamp flashes 3 times and the right lamp of OPERATION INDICATOR
lamp is not lighted.
Indoor fan does not operate.

A

Check of indoor fan motor

The indoor fan motor error has occurred, and the indoor fan does not operate.

Turn OFF the power supply.

Is there anything that interferes the
rotation of the line flow fan?

Yes

Remove the object and
adjust the line flow fan.

Is there 311V DC between
CN211 (+) and (-), and does
the voltage between CN211 (+)
and (-) rise to the range between 3
and 6V DC within 12 seconds after
EMERGENCY OPERATION switch
is pressed?

No

Replace the indoor electronic control P.C. board.

No

Pay careful attention to the high voltage on
the fan motor connector CN211.

Turn ON the power supply, wait 5 seconds or more, and then press
EMERGENCY OPERATION switch.
Measure the supply voltage as follows within 12 seconds
after EMERGENCY OPERATION switch is pressed.
If more than 12 seconds passes by, turn OFF the power supply and
turn ON it again, then measure the voltage.

1) Measure the voltage between CN211 (+) and (-).

2) Measure the voltage between CN211 (+) and (-).

If more than 12 seconds passes after EMERGENCY OPERATION switch
is pressed, the voltage mentioned in above 2) goes 0V DC although the
indoor electronic control P.C. board is normal.

Indoor electronic

Yes

Replace the indoor fan motor.

Fuse (F11)

VARISTOR (NR11)

R111

control P.C. Board

JR05

IC101

T11

C111

JR06

CN151

CN211

The indoor fan motor error has occurred, and the indoor fan repeats "12-second ON and 30-second OFF" 3 times, and then stops.

Measure the voltage between CN211
(+) and (-) while the fan
motor is rotating.

Is 0V DC or 15V DC
held unchanged?

Yes
(Unchanged)

Replace the indoor fan motor.

No
(Changed)

Replace the indoor electronic control P.C. board.

24

Indoor unit operates by pressing EMERGENCY OPERATION switch, but does not operate with the remote controller.

Check of remote controller and receiver P.C. board B

Check if the remote controller is exclusive for this air conditioner.

Press OPERATE/STOP (ON/OFF) button on the remote controller.

Is the LCD display on the the
remote controller visible?

Yes

Remove the batteries, then set them back
and press RESET button. (Refer to 10-1.4.)
Check if the unit operates with the remote
controller.

Does the unit operate with the
remote controller?

Yes

OK

No

(not clear)

No

Replace the batteries. (Refer to 10-1.4.)

Turn on a radio to AM and press
OPERATE/STOP (ON/OFF) button
on the remote controller.

Is noise heard from radio?

Yes

Are there any fluorescent lights of
inverter or of rapid-start type within
the range of 1m?

No

Replace the indoor electronic
control P.C. board.

No

Yes

Replace the remote controller.

● Reinstall the unit away from lights.

● Attach a filter on receiving part.

25

The unit cannot be operated with the remote controller.
Also, OPERATION INDICATOR lamp does not light up by pressing EMERGENCY OPERATION switch.

Check of indoor electronic control P.C. board and indoor fan motor

C

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.

Does the unit operate with the remote controller?
Does OPERATION INDICATOR lamp light up by
pressing EMERGENCY

OPERATION switch?

No

Turn OFF the power supply.
Measure the resistance between CN211
and of the indoor fan motor connector.

Yes

Turn OFF the power supply.
Measure the resistance of the horizontal vane
motor coil and the vertical vane motor coil.
Refer to 10-5.

Replace the varistor (NR11) and fuse (F11).

Yes

Short/ open circuit:
Replace the indoor fan motor.

Short/ open circuit:
Replace the horizontal vane motor, the vertical
vane motor coil and the indoor electronic
control P.C. board.

Turn OFF the power supply.
Check both “parts side” and “pattern
side” of the indoor electronic control P.C.
board visually.

Indoor electronic
control P.C. Board

Fuse (F11)

VARISTOR (NR11)

Are the varistor (NR11) burnt
and the fuse (F11) blown?

Be sure to check both the fuse
and the varistor in any case.

Is the fuse (F11) blown only?

Measure the resistance between
(+) and (-) of the indoor fan
motor connector (to CN211 on the
indoor electronic control P.C. board).
1, 2

Is the resistance 1MΩ
or more?

Replace the fuse (F11).

Measure the cement resistance R111 on
the indoor electronic control P.C. board.

JR06

JR05

IC101

No

No

Yes

1. The fan motor connector's lead wire is red, whereas is black.

2. Connect "+" of the tester to fan motor connector's lead
wire, and "-" to lead wire, otherwise the resistance cannot be
measured properly.

No

Replace the fuse (F11) and the indoor fan motor.

Yes

Is the resistance
approx. 4Ω?

Yes

Replace the indoor electronic control P.C. board.

No

Replace the indoor electronic control P.C. board
and the indoor fan motor.

R111

C111

T11

CN151

CN211

26

When the left lamp of OPERATION INDICATOR lamp flashes ON and OFF in every 0.5-second.
Outdoor unit does not operate.

D

How to check mis-wiring and serial signal error

Turn OFF the power supply.

Is there rated voltage of
230V AC in the power
supply?

Yes

Turn ON the power supply.

Is there 230V AC between
outdoor terminal block S1 and
S2?

Yes

Press EMERGENCY OPERATION switch once.

Does the left lamp of OPERATION INDICATOR
lamp light up? <Confirmation of the power
supply to the indoor unit>

Yes

Is the serial signal error indicated 6 minutes later?

Yes

No

No

Check the power
supply.

Check the wiring.

No

Is there any mis-wiring,
poor contact, or wire

No

disconnection of the
indoor/outdoor
connecting wire?

No

Yes

Correct them.

· Turn OFF inverter-controlled lighting equipment.

· Turn OFF the power supply and then turn it ON again.

· Press EMERGENCY OPERATION switch.

Is the serial
signal error
indicated 6
minutes later?

Yes

Turn OFF the power supply.
Check once again if the indoor/outdoor
connecting wire is not wrongly connected.

Short-circuit the outdoor terminal block S2
and S3.
1

No

· Reinstall either the unit or the light away
from each other.

· Attach a filter on receiving section of the indoor unit.

1. Mis-wiring may damage indoor electronic control
P.C. board during operation.
Be sure to confirm the wiring is correct before the
operation starts.

As for outdoor unit, refer to outdoor unit service manual.

27

When the left lamp of OPERATION INDICATOR lamp flashes 9-time.
Indoor unit and outdoor unit do not operate.

Check of float sensor

E

Indoor electronic control P.C. board

Connect the lead wire.

*1 Refer to 10-5. when
float sensor can be checked.

Yes

Turn OFF the power supply and check
connectors CN145 and CN1N1 visually.

Are the lead wires
disconnected?

No

Disconnect float sensor from CN145 of
indoor electronic control P.C. board.
Measure the resistance between and .

Turn ON the power supply. Press
EMERGENCY OPERATION switch
(COOL) and perform emergency COOL
operation. Measure the voltage between
CN1N1 and .

Are there abnormality in
the soldering part of
connectors?

Is the resistance 1Ω or
less? *1

No

Is there large amount
of water in drain pan?

Yes

Is there 230V AC
between CN1N1 and
?

Is the drain pump
operating?

Is the drain hose
clogged?

Replace the indoor
electronic control P.C. board.

Yes

Yes

No

Yes

Yes

No

No

No

Yes

No

Replace the indoor
electronic control P.C. board.

Replace the float sensor.

Replace the indoor
electronic control P.C. board.
Check power supply voltage.

Replace the drain pump.

Remove clog from drain
hose.

CN145

CN1N1

Solder the connector.

28

Electromagnetic noise enters into TV sets or radios

F

Is the unit earthed?

Yes

Is the distance between the
antennas and the indoor
unit within 3m, or is the
distance between the
antennas and the outdoor
unit within 3m?

No

Is the distance between the
TV sets or radios and the
indoor unit within 1m, or is
the distance between the TV
sets or radios and the
outdoor unit within 3m?

No

Are the antennas damaged?
Is the coaxial cable damaged?
Is there any poor contact in
the antenna wiring?

No

Is the indoor/outdoor
connecting wire of the air
conditioner and the wiring of
the antennas in close?

No

Yes

Yes

Yes

Yes

Earth the unit.

Extend the distance between
the antennas and the indoor
unit, or the antennas
and the outdoor unit.

Extend the distance between
the TV sets or radios and the
indoor unit, or the TV
sets or radios and the
outdoor unit.

Replace or repair the antenna.
Replace or repair the coaxial cable.

Extend the distance between
the indoor/outdoor connecting
wire of the air conditioner and
the wiring of the antennas.

No

Even if all of the above conditions is fulfilled, the electromagnetic noise may enter, depending on
the electric field strength or the installation condition (combination of specific conditions such as
antennas or wiring).
Check the followings before asking for service.

1.Devices affected by the electromagnetic noise
TV sets, radios (FM/AM broadcast, shortwave)

2.Channel, frequency, broadcast station affected by the electromagnetic noise

3.Channel, frequency, broadcast station unaffected by the electromagnetic noise

4.Layout of ;
indoor/outdoor unit of the air conditioner, indoor/outdoor wiring, grounding wire, antennas, wiring
from antennas, receiver

5.Electric field intensity of the broadcast station affected by the electromagnetic noise

6.Presence or absence of amplifier such as booster

7.Operation condition of air conditioner when the electromagnetic noise enters in.

1)Turn OFF the power supply once, and then turn ON the power supply. In this situation check for
the electromagnetic noise.

2)Within 3 minutes after turning ON the power supply, press OPERATE/STOP (ON/OFF) button
on the remote controller for power ON, and check for the electromagnetic noise.

3)After a short time (3 minutes later after turning ON), the outdoor unit starts running. During
operation, check for the electromagnetic noise.

4)Press OPERATE/STOP (ON/OFF) button on the remote controller for power OFF, when the
outdoor unit stops but the indoor/outdoor communication still runs on. In this situation check for
the electromagnetic noise.

After checking the above, consult the service representative.

29

10-7. TEST POINT DIAGRAM AND VOLTAGE

MLZ-KA25VA MLZ-KA35VA MLZ-KA50VA

Indoor electronic control P.C. board

CN111
Room temperature

F11 FUSE
T3.15AL 250V

NR11

Varistor

CN202
Serial
signal

thermistor RT11

CN201
Power supply
input 230V AC

5V DC

CN112

Indoor coil thermistor RT14 (MAIN 2) [MLZ-KA50VA]

Indoor coil thermistor RT13 (SUB)

Indoor coil thermistor RT12 (MAIN 1)

CN113

Indoor coil thermistor RT15 (MAIN 3) [MLZ-KA50VA]

Dip switch SW3
(Increase air flow volume)

Release of Auto reset
function
Solder the Jumper
wire to JR07. (Refer to 8-3.)

Timer short mode point

}

JPG, JPS (Refer to 8-1.)

Emergency operation switch

CN145
Float
sensor

CN1N1
Drain
pump

R111

JR05

JR06

}

Modification point for
individual operation
(Refer to 8-2.)

GND DC 12V DC

CN151
Horizontal vane motor

Vertical vane motor

Indoor fan motor CN211

over 15V DC
3-6V DC
15V DC

311V DC

Indoor coil thermistor [RT12,RT14,RT15 (MAIN), RT13 (SUB)]
Room temperature thermistor (RT11)

30

Resistance (kΩ)

Temperature (ºC)

11

DISASSEMBLY INSTRUCTIONS

<"Terminal with locking mechanism" Detaching points>

The terminal which has the locking mechanism can be detached as shown below.
There are two types ( Refer to (1) and (2)) of the terminal with locking mechanism.
The terminal without locking mechanism can be detached by pulling it out.
Check the shape of the terminal before detaching.

(1) Slide the sleeve and check if there is a locking lever or not.

Sleeve

Slide the sleeve.
Pull the terminal while

Locking lever

pushing the locking
lever.

MLZ-KA25VA MLZ-KA35VA MLZ-KA50VA
INDOOR UNIT

OPERATING PROCEDURE

1. Opening the intake grille

(1) Press the area indicated “PUSH” on the intake grille until a

click is heard (Figure 1).

(2) Hold the tabs on both sides of the intake grille and pull it

down.

2. Removing the intake grille

(1) Press the area indicated “PUSH” on the intake grille until a

click is heard.

Hold the tabs on both sides of the intake grille and pull it

down (Figure 1).
(2) Pull the hinges of the intake grille toward you (Figure 2).
(3) Unhook the safety strings supporting the intake grille from

the front panel (Figure 3).

Figure 1

(2) The terminal with this connector has the
locking mechanism.

Photo 1

Places for installing
the Anti-Allergy Enzyme filter (Option)

Remote
control
receiving
section

Electrical
box

Safety strings for
preventing the
intake grille from
falling

Hold the sleeve, and
pull out the terminal
slowly.

Connector

PHOTOS

Places for installing
the air filters
(Catechin air filter, option)

Intake grille

Figure 2

Figure 3

31

OPERATING PROCEDURE PHOTOS

3. Checks before setting in place

(1) Before installing the grille, make sure the indoor unit is

square with the ceiling opening (or parallel to the wall-ceiling joint).

(2) Check that the four points for securing the grille are in

contact with the ceiling surface. Use the installation
template supplied with the indoor unit to arrange the four
points for securing the grille within 0 to 3 mm from the
ceiling surface (Figure 4, 5).

(3) Check that the insulation for the refrigerant pipes, drain

pipes, etc. are in place and that wiring connections and
arrangements are complete.

4. Removing the horizontal vane

(1) Slide each stopper of the horizontal vane.
(2) Remove the horizontal vane (Figure 6).

NOTE:

To install, follow the removal procedure in reverse.
Make sure a click is heard from each stopper when
attaching the vane.

5. Removing the grille

(1) Open the intake grille.
(2) Remove the screw cap in the center of air outlet
(Figure 8).
(3) Remove the fixing screws ( and in Figure 7).
(4) Remove the temporary holding tabs of the grille.

Figure 4

Figure 5

Ceiling surface

Figure 6

Points for securing the grille

Points for securing the grille

Drain pan

Make sure
that these
surfaces are
flush with
each other.
(0~3 mm)

Places for
securing
the grille

Close-up

Make sure
that these
surfaces are
flush with
each other.
(0~3 mm)

Stopper

6. Installing the grille

(1) Press the areas indicated “PUSH” on the intake grille

to open.
(2) Remove the screw cap in the center of air outlet.
(3) Open the horizontal vane completely.
(4) Hook the temporary holding tabs of the grille to the

indoor unit (Figure 7).
(5) Place the grille so that it fits properly in the

wall-ceiling joint, and attach the front panel with the fixing

screws provided. Do not fully tighten the screws at this

point.
(6) Tighten the fixing screws in the center three places and

(Figure 7).

(7) Tighten the fixing screws in the four places at left and

right side of the indoor unit.

At this point, make sure there are no gaps between the indoor

unit and grille, and between the grille and ceiling surface. If
there are gaps, the wind may come in and it may cause water
to drip (Figure 9).

Tighten the fixing screw and completely.

Installing the Anti-Allergy Enzyme filter (Option)
Push the Anti-Allergy Enzyme filter into the guide of the grille

until a click is heard (Figure 10).

Horizontal vane

Figure 7

Figure 8

Hooks

Temporary holding tabs

Screw cap

32

Screw cap

OPERATING PROCEDURE PHOTOS

Anti-Allergy Enzyme filter (Option)

7. Check after installing

(1) Check that there are no gaps between the indoor unit and

grille, and between the grille and ceiling surface (Figure 9).
(If there are gaps, the wind may come in and dew
condensation may result.)
(2) Is the air filter installed?
(3) Is the Anti-Allery Enzyme filter (Option) installed?

8. Removing the electronic control P.C. board and
display receiver P.C. board

(1) Open the intake grille.
(2) Remove the screws for the electrical cover and .

Remove the covers (Photo 2).
(3) Remove the screw for the lamp cover and unhook it.
(4) Pull the electronic control P.C. board slightly toward you

from the electrical box, and disconnect all the connectors

from the electronic control P.C. board.
(5) Remove the electronic P.C. board and display receiver P.C.

board.

9. Removing the heat exchanger and nozzle

(1) Remove the grille.
(2) Remove the room temperature thermistor.
(3) Remove the two claws in the center of the nozzle and the

screws for the drain pan.
(4) Remove the screws for the electrical cover and .

Remove both covers.
(5) Disconnect the connectors of the vertical and horizontal

vane motor.
(6) Remove the indoor coil thermistor (main and sub.).
(7) Remove the screws for the drain cover. Remove the drain

cover.
(8) Remove the pipe band.
(9) Remove the screws for the heat exchanger. Remove the

heat exchanger.
(10)

Remove the screws for the nozzle. Remove the nozzle.

10. Removing the horizontal and vertical vane motor
unit

(1) Remove the grille.
(2) Remove the drain pan.
(3) Remove the horizontal vane (Figure 6).
(4) Remove the screws for the cover of the horizontal and

vertical vane motor unit. Remove the cover.
(5) Remove the screws for the vertical vane motor unit.

Remove the vertical vane motor unit and disconnect the

connectors (Photo 4).
(6) Remove the screws for the horizontal vane motor unit.

Remove the horizontal vane motor unit and disconnect the

connectors (Photo 4).

Figure 9

Ceiling surface Grille

Indoor unit

No gaps here

Figure 10

Photo 2

Electrical cover

Drain pan

Screws for the electrical cover

Photo 3

Drain cover

Float sensor

Room temperature thermistor

Screw for the
electrical over

Electrical cover

Screw for the
lamp cover

Lamp cover

Screw for the
electrical cover

Indoor heat
exchanger

33

Drain pump

Nozzle

Cover of the horizontal
and vertical vane motor

OPERATING PROCEDURE PHOTOS

11. Removing the drain pump and float sensor

(1) Remove the grille.
(2) Remove the drain pan.
(3) Disconnect the connector of the drain pump (Photo 5).
(4) Disconnect the connector of the float sensor (Photo 5).
(5) Remove the drain hose (Photo 5).
(6) Remove the screws for the drain pump (Photo 5).
(7) Remove the screws for the cover of the drain pump

(Photo 5).

12. Removing the fan motor and line flow fan

(1) Remove the grille.
(2) Remove the drain pan.
(3) Remove the drain cover.
(4) Remove the pipe band.
(5) Remove the screws for the electrical cover

Remove both covers.

(6) Remove the screws for the terminal box. Remove the

terminal box.
(7) Untie the safety strings from the clamp (Photo 6).
(8) Hook the safety strings to the tab on the side of the heat

exchanger. (This prevents the heat exchanger from

falling.) Remove the screws for the heat exchanger and

pull the heat exchanger downward.
(9) Remove the screws for the nozzle. Remove the nozzle.
(10)

Pull out the electronic control P.C. board slightly and

disconnect the connector (CN211) of the indoor fan motor.
(11)

Remove the screws for the motor band. Remove the

motor band (Photo 6).
(12)

Remove the indoor fan motor and line flow fan. (No need

to remove the heat exchanger before removing these 2

items.)

and .

Photo 4

Vertical vane motor

Photo 5

Screws for
the drain
pump

Drain pump

Screws for the
cover of the
drain pump

Photo 6

Nozzle

Drain hose

Connector for
the float sensor

Fan motor

Horizontal vane motor

Float sensor

Cover of the
drain pump

Screws for
the cover
of the drain
pump

Screws for
the drain
pump

Connector for
the drain pump

Safety string

34

Line flow fan

Motor band

Safety string

Screws for the motor band

35

HEAD OFFICE: TOKYO BLDG., 2-7-3, MARUNOUCHI, CHIYODA-KU, TOKYO100-8310, JAPAN

Copyright 2007 MITSUBISHI ELECTRIC ENGINEERING CO.,LTD
Distributed in Nov. 2009 No. OBH483 REVISED EDITION-A 7
Distributed in Feb. 2007. No. OBH483 8
Made in Japan

New publication, effective Nov. 2009
Specifications subject to change without notice.