MUZ-FH Service

35
No. Symptom LED indication
Abnormal point/
Condition
Condition Remedy
16
Outdoor unit
operates.
1-time fl ash
2.5 seconds OFF
Frequency drop by
current protection
FH06/09/12
When the input current exceeds approximately
10A (FH06/09)/10.5A (FH12), compressor fre-
quency lowers.
The unit is normal, but check the
following.
•
Check if indoor fi lters are clogged.
•
Check if refrigerant is short.
•
Check if indoor/outdoor unit air
circulation is short cycled.
FH15/18 Current from power outlet is nearing breaker ca-
pacity.
17
3-time fl ash
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 fl ash
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
MUZ-FH06/09/12
5-time fl ash
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
Outdoor unit
operates.
7-time fl ash
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 fl ash
2.5 seconds OFF
MUZ-FH06/09/12
PAM protection
PAM: Pulse Ampli-
tude Modulation
The overcurrent fl ows into PFC (Power factor correction
:IC820) or the DC voltage reaches 394 V 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.
MUZ-FH15/18
Zero cross detecting
circuit
Zero cross signal cannot be detected.
•
It occurs with following cases.
1 Instantaneous power voltage
drop. (Short time power failure)
2 Distortion of primary voltage
•
Refer to 10-5.
"Check of power
supply".
22
9-time fl ash
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 fi gure. Refer to 10-6.1.
2. LED is lighted during normal operation.
The fl ashing frequency shows the number of times the LED blinks after every 2.5-second OFF.
(Example) When the fl ashing frequency is “2”.
ON
OFF
2.5-second OFF
2.5-second OFF
0.5-second ON
0.5-second ON
LED
Flashing →
MUZ-FH06/09/12
Inverter P.C. board
MUZ-FH15/18
LED
→
Flashing
OBH684D