Service Manual

88
No. Symptom
Indication
Abnormal point / Con-
dition
Condition Remedy
LED1(Red) LED2(Yellow)
22 'Outdoor unit
stops and
restarts
3 minutes
later' is
repeated.
11 times Not lit
Low out side tempera
-
ture protection(cooling)
The ambient became 10.4°F or less.
—
Low out side tempera-
ture protection(Heating)
The ambient became 1.4°F or less. (MXZ-3C24/3C30/
4C36/5C42NA, MXZ-3C24/3C30/4C36/5C42NA2)
The ambient became -18°F or less. (MXZ-2C20/
3C24/3C30NAHZ, MXZ-2C20/3C24/3C30NAHZ2)
23
13 times Not lit Outdoor fan motor
A failure occurs 3 consecutive times within 30
seconds after the fan gets started.
• Refer to 12-6.
"Check of outdoor fan motor".
24
14 times Not lit
4-way valve switching
operation
Connector of R.V. coil is disconnected, poorly con-
nected or 4-way valve is faulty.
• Refer to 12-6.
"Check of R.V. coil".
• Check the 4-way valve.
25
Lit 8 times
Current sensor protec-
tion
A
short or open circuit is detected in the current
sensor during compressor operating.
• Replace the outdoor power P
.C. board.
26
Lit 11 times
Communication
between P.C. boards
protection
Communication error occurs between the outdoor
control P.C. board and outdoor power P.C. board
for more than 10 seconds.
• Check the connecting wire between outdoor con
-
trol P.C. board and outdoor power P.C. board.
27
Lit 12 times
Zero cross detecting
circuit protection (Out-
door power P.C. board)
Zero cross signal cannot be detected while the
compressor is operating.
• Replace the outdoor power P
.C. board.
28 Outdoor unit
operates.
Once Lit
Primary current protec
-
tion
The input current exceeds
15.0 A (MXZ-2C20NA2)
/18.4 A (MXZ-3C24/3C30/4C36NA, MXZ-3C24/3C30/
4C36NA2)
/26.8 A (M
XZ-2C20/3C24/3C30NAHZ, 5C42NA,
MXZ-2C20/3C24/3C30NAHZ2, MXZ-5C42NA2)
.
These symptoms do not mean any abnormality of
the product, but check the following points.
• Check if indoor lters are clogged.
• Check if refrigerant is short.
• Check if indoor/outdoor unit air circulation is short
cycled.
29
Twice Lit
High pressure protec
-
tion
The indoor gas pipe temperature exceeds 113°F
during heating.
Defrosting in cooling
The indoor gas pipe temperature falls 37.4°F or
below during cooling.
30
3 times
Lit
Discharge temperature
protection
The frequency of the compressor is kept 80 Hz or
more and the discharge temperature is kept under
122°F(COOL mode)/104°F(HEAT mode) for more
than 40 minutes.
• Check refrigerant circuit and refrigerant amount.
• Refer to 12-6.
"Check of LEV".
• Refer to 12-6.
"Check of outdoor thermistors".
31
4 times Lit
Low discharge
temperature protection
The frequency of the compressor is kept 80 Hz or
more and the discharge temperature is kept under
102.2°F for more than 20 minutes.
• Refer to 12-6.
"Check of LEV".
• Check refrigerant circuit and refrigerant amount.
32
5 times Lit
Cooling high pressure
protection
The outdoor heat exchanger temperature exceeds
136.4°F during operation.
This symptom does not mean any abnormality of
the product, but check the following points.
• Check if indoor lters are clogged.
• Check if refrigerant is short.
•
Check if indoor/outdoor unit air circulation is short cycled.
33
7 times Lit
High Low
Pressure bypass
valve
Cooling evaporating
temperature drop
prevention control
During cooling operation, the temperature of indoor
heat exchanger becomes 37.4°F or less within 1
hour after the compressor starts running, or it be
-
comes less than 53.6°F - 60.8°F* later than that.
* It depends on the di󰀨erence between the set
temperature and the room temperature.
(MXZ-2C20/3C24/3C30NAHZ, MXZ-5C42NA,
MXZ-2C20/3C24/3C30NAHZ2, MXZ-5C42NA2)
This symptom does not mean any abnormality of
the product, but check the following points.
• Check the indoor lters are not clogged.
• Check there is su󰀩cient refrigerant.
• Check the indoor/outdoor unit air circulation is not
short cycled.
34
11 times Lit
M-NET communication
error
M-NET adapter P.C. board detects an abnormality
in the communication error.
• Check the connecting wire between M-NET
adapter P.C. board and outdoor control P.C.
board, or terminal block.
35
Outdoor
unit
operates
normally.
7 times Lit
High Low
pressure bypass valve
High pressure protec
-
tion control at startup of
heating operation
The room
temperature is 75.2°F or more when 1 or
2 unit(s) start(s) the heating operation.
(MXZ-2C20/3C24/3C30NAHZ, MXZ-5C42NA,
MXZ-2C20/3C24/3C30NAHZ2, MXZ-5C42NA2)
This symptom does not mean any abnormality of
the product.
High
Low
pressure bypass valve
Compressor oil temper
-
ing control at startup of
heating operation
Both the following are true:
• The
outside temperature is 28.4°F or less when
the heating operation is started.
• [(Discharge temperature) - (Indoor heat exchang
-
er temperature)] < 9°F
(MXZ-2C20/3C24/3C30NAHZ, MXZ-5C42NA,
MXZ-2C20/3C24/3C30NAHZ2, MXZ-5C42NA2)
36
8 times Lit
Cooling evaporating
temperature
protection
During cooling operation, the temperature of
indoor heat exchanger becomes 44.6°F - 51.8°F*
or less within 1 hour after the compressor
starts running, or it becomes 48.2°F - 62.6°F* or
less later than that.
* It depends on the indoor unit type/model or the
di󰀨erence between the set temperature and the
room temperature.
37
9 times Lit Inverter check mode
The unit is operated with emergency operation
switch.
—
38 Lit Lit Normal — —
NOTE: 1. The location of LED is illustrated at the right figure. Refer to 12-7.1.
2. LED is lit during normal operation.
The blinking frequency shows the number of times the LED blinks after every 2.5-second OFF.
(Example) When the blinking frequency is “2”.
ON
OFF
2.5-second OFF
2.5-second OFF
0.5-second ON
0.5-second ON
LED1
LED2
Lit
Outdoor control P.C. board
(Parts side)
OBH702H