Mitsubishi Electric MUZ-HE09NA, Service Manual, Page: 37 / 62

37
No. Symptom LED indication
Abnormal point/
Condition
Condition Remedy
19
Outdoor
unit oper-
ates.
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 the refrigerant circuit and the
refrigerant amount.
•
•
20
8-time fl ash
2.5 seconds OFF
PAM protection PAM:
Pulse Amplitude
Modulation
The overcurrent fl ows into IGBT (Insulated Gate Bipolar transis-
tor: TR821) or the bus-bar voltage reaches 320 V or more, PAM
stops and restarts.
This is not malfunction. PAM protection
will be activated in the following cases:
1 Instantaneous power voltage drop
(Short time power failure)
2 When the power supply voltage is high.
Zero cross detecting
circuit
Zero cross signal for PAM control cannot be detected.
21
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 compres-
sor is correctly connected. Refer to
10-5. "How to check inverter/compres-
sor".
•
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. Flashing
(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 →
LED
MUZ-HE24NA
MUZ-HE09/12/15/
18NA
Inverter
P.C. board
(Parts side)
OBH686