Mitsubishi Electric MXZ-SM72TAM-U1 Service Manual page 44

1501 (U2): Refrigerant shortage trouble
Abnormal points and detection methods
• All of the following conditions have been satisfied for 15
consecutive minutes:
- The compressor is operating in HEAT mode.
- Discharge superheat is 144°F (80°C) or more.
- Difference between TH7 and TH3 fits the formula of
TH7−TH3 < 9°F (5°C)
- The saturation temperature converted from the pres-
sure detected by the high pressure sensor is below
95°F (35°C).
• All of the following conditions have been satisfied:
- The compressor is in operation.
- When cooling, discharge superheat is 144°F (80°C)
or more, and the saturation temperature converted
from the pressure detected by the high pressure
sensor is over −40°F (−40°C).
- When heating, discharge superheat is 162°F (90°C)
or more.
Diagnosis of failure
Is the outdoor stop valve (ball valve)
fully open?
Is there refrigerant leak?
Is the error code 5104 displayed when
restarted?
Check relevant thermistor wirings and connector
contacts of the outdoor multi controller circuit
board.
Is there any abnormality on connec-
tors such as disconnection, half-dis-
connection or breakage?
Disconnect the thermistor wiring and check the
resistance.
Continue to the next page.
OCH800A_44
No
Yes
Yes
No
Yes
(5104)
No
(1501)
Yes
No
Causes and checkpoints
• Defective operation of stop valve (not fully open)
• Defective thermistor
• Defective outdoor multi controller circuit board
• Indoor LEV performance failure
• Gas leakage or shortage
• Defective 63HS
TH3:
Thermistor <Outdoor liquid pipe>
TH7:
Thermistor <Ambient>
LEV:
Linear expansion valve
63HS:
High pressure sensor
Open the stop valve (ball valve) fully.
Repair the refrigerant leak.
Refer to the diagnosis of error code 5104.
Connect the connector properly
(Repair or replace it in the case of breakage).
Chart 1 of 2