Low Pressure Error Or Low Pressure Sensor Anomaly - Mitsubishi Heavy Industries FDT71VNXWVH Service Manual

Error code
Indoor control PCB
Remote control:
E49
Outdoor control PCB
Outdoor inverter
1. Applicable model
2. Error detection method
Detected by low pressure drop
and suction superheat
3. Condition of error displayed
➀ When the low pressure sensor
detects 0.079MPa or lower
for 15 seconds continuously,
compressor stops and it
restarts automatically after
3-minute delay. And if this
anomaly occurs 3 times
within 60 minutes.
➁ 10 minutes after the
compressor starts, if the
low pressure sensor detects
0.15MPa or lower for 60
minutes continuously and
compressor suction superheat
is detected 30degC or higher
for 60 minutes continuously.
And if this anomaly occurs 3
times within 60 minutes.
➂ If low pressure sensor
detects 0.079MPa or lower
for 5 minutes continuously
(including the compressor
stop status).
4. Presumable cause
• Defective outdoor unit control
PCB
• Defective low pressure sensor
connector
• Defective low pressure sensor
• Defective suction pipe
temperature sensor connector
• Defective suction pipe
temperature sensor
Note:
* Connect the gauge manifold to the service valve check joint during cooling, or connect it to the check joint at internal
piping of outdoor unit during heating.
LED Green
Keeps flashing
Keeps flashing
Yellow LED
PCB
Keeps flashing
5. Troubleshooting
pressure sensor connection OK
Check the low pressure value during
following state from the remote control
ΠCompressor is stopping
 Compressor is operating
pressure detected at around 0MPa
NO
Check the insulation resistance of pressure sensor.
insulation resistance more than 100M ?
After connecting the gauge manifold on the low pressure
line, measure at the state Πabove. Compare the result
with the value indicated on the remote control.
pressure difference less than
To checking of refrigerant
amount, refrigerant circuit,
etc.
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Red
Content
Stays OFF
Low pressure error or
1-time flash
low pressure sensor anomaly (1/2)
Diagnosis
Is the low
(at PCB side)?
YES
During
both Œ and  state low
without any
fluctuation.
YES
Is the
at DC500V?
YES
Is the
NO
0.2MPa?
Connect the pressure sensor of
YES
spare part to outdoor control
PCB in the condition open to
atmosphere.
Is the pressure
0MPa displayed on the remote
control?
112
- -
'19 • PAC-SM-332
Countermeasure
Correct.
NO
Replace low pressure
NO
sensor.
Defective outdoor unit
NO
control PCB ➞ Replace.
Replace low pressure
YES
sensor.