Mitsubishi Electric MXZ-2C20NA2-U1, Service Manual

Page: 84 / 114

84
No. Symptom
Indication
Abnormal point / Con-
dition
Condition Remedy
LED1(Red) LED2(Yellow)
21 '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. (
0;=&&
&&1$0;=&&&&1$
)
The ambient became -18°F or less. (
0;=&
&&1$+=0;=&&&1$+=
)
22
13 times Not lit Outdoor fan motor
A failure occurs 3 consecutive times within 30
seconds after the fan gets started.
• Refer to 11-6. "Check of outdoor fan motor".
23
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.
24
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.
25
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.
26 Outdoor unit
operates.
Once Lit
Primary current protec-
tion
The input current exceeds 15.0 A (
MXZ-2C20NA2
)
18.4 A (
0;=&&&1$0;=&&
4C36NA2
)/26.8 A (
0;=&&&1$+=&1$
0;=&&&1$+=0;=&1$
).
These symptoms do not mean any abnormality of
the product, but check the following points.
‡&KHFNLILQGRRU¿OWHUVDUHFORJJHG
• Check if refrigerant is short.
• Check if indoor/outdoor unit air circulation is short
cycled.
27
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.
28
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 11-6. "Check of LEV".
• Refer to 11-6. "Check of outdoor thermistors".
29
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 11-6. "Check of LEV".
• Check refrigerant circuit and refrigerant amount.
30
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.
‡&KHFNLILQGRRU¿OWHUVDUHFORJJHG
• Check if refrigerant is short.
• Check if indoor/outdoor unit air circulation is short cycled.
31
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 difference between the set
temperature and the room temperature.
(
0;=&&&1$+=0;=&1$
0;=&&&1$+=0;=&1$
)
This symptom does not mean any abnormality of
the product, but check the following points.
‡&KHFNWKHLQGRRU¿OWHUVDUHQRWFORJJHG
‡&KHFNWKHUHLVVXI¿FLHQWUHIULJHUDQW
• Check the indoor/outdoor unit air circulation is not
short cycled.
32
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.
33 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.
(
0;=&&&1$+=0;=&1$
0;=&&&1$+=0;=&1$
)
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
(
0;=&&&1$+=0;=&1$
0;=&&&1$+=0;=&1$
)
34
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
difference between the set temperature and the
room temperature.
35
9 times Lit Inverter check mode
The unit is operated with emergency operation
switch.
—
36 Lit Lit Normal — —
NOTE
: 1. The location of LED is illustrated at the right figure. Refer to 11-7.1.
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)
OBH702G