43
No.
Symptom
LED indication
Abnormal point/
Condition
Condition
Remedy
16
Outdoor unit
operates.
1-time blink
2.5 seconds OFF
Frequency drop by
current protection
Current from power outlet is nearing Max. fuse size.
The unit is normal, but check the
following.
•
Check if indoor filters are clogged.
• Check if refrigerant is short.
• Check if indoor/outdoor unit air
circulation is short cycled.
17
3-time blink
2.5 seconds OFF
Frequency drop by
high pressure pro-
tection
Temperature of indoor coil thermistor exceeds 131 °F (55°C)
in HEAT mode, compressor frequency lowers.
Frequency drop by
defrosting in COOL
mode
Indoor coil thermistor reads 46°F (8°C) or less in COOL mode,
compressor frequency lowers.
18
4-time blink
2.5 seconds OFF
Frequency drop by
discharge tempera-
ture protection
Temperature of discharge temperature thermistor exceeds
232°F (111°C), compressor frequency lowers.
• Check refrigerant circuit and refrig-
erant amount.
• Refer to 10-5. "Check of LEV".
• Refer to 10-5. "Check of outdoor
thermistors".
19
5-time blink
2.5 seconds OFF
Outside temperature
thermistor protec-
tion
When the outside temperature thermistor shorts or opens,
protective operation without that thermistor is performed.
• Refer to 10-5. Check of outdoor
thermistors.
20
7-time blink
2.5 seconds OFF
Low discharge tem-
perature protection
Temperature of discharge temperature thermistor has been
122°F (50°C) or less for 20 minutes.
• Refer to 10-5. "Check of LEV".
• Check refrigerant circuit and refrig-
erant amount.
21
8-time blink
2.5 seconds OFF
PAM protection
PAM: Pulse Ampli-
tude Modulation
The overcurrent flows into IGBT (Insulated Gate Bipolar tran
-
sistor: TR821) (
MUZ-HM09/12NA(2) -
U8
)/PFC (Power factor
correction: IC820) (
MUZ-HM09/12/15/18/24NA(2) -
U1
MUZ-
HM09/12/15/18/24NAH MUZ-HM09/12/15/18NA -
U2
MUZ-
HM24NAH
) or the bus-bar voltage reaches 320 V (
MUZ-
HM09/12NA(2) -
U8
)/394 V (
MUZ-HM09/12/15/18/24NA(2) -
U1
MUZ-HM09/12/15/18/24NAH MUZ-HM09/12/15/18NA -
U2
)
or more, PAM stops and restarts.
This is not malfunction. PAM pro-
tection will be activated in the fol-
lowing cases:
1 Instantaneous power voltage
drop. (Short time power failure)
2 When the power supply voltage
is high.
Zero cross detecting
circuit
(
MUZ-HM09/12NA(2)
MUZ-HM09/12NAH
)
Zero cross signal for PAM control cannot be detected.
22
9-time blink
2.5 seconds OFF
Inverter check mode The connector of compressor is disconnected, inverter check
mode starts.
• Check if the connector of the com-
pressor is correctly connected.
Refer to 10-5. "How to check
inverter/compressor".
NOTE:
1. The location of LED is illustrated at the right figure. Refer to 10-6.1.
2. LED is lighted during normal operation.
3. Blinking patterns of this mode differ from the ones of the failure recall mode.
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
LED
Blinking →
Inverter P.C. board
LED
Blinking →
MUZ-HM09/12NA2
MUZ-HM09/12NA -
U1
-
U2
MUZ-HM09/12NAH
MUZ-HM15/18/24NA(2)
MUZ-HM15/18/24NAH
Inverter P.C. board
LED
Blinking →
MUZ-HM09/12NA -
U8
OBH747F
