Low Pressure Error - Mitsubishi Heavy Industries FDT100VNAWVH Service Manual

Error code
Remote control:
E49
Indoor unit
control PCB
Outdoor unit
control PCB
1. Applicable model
All models
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 5 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 seconds continuously.
And if this anomaly occurs 5
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 main
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
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 (1/2)

1-time flash
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 unit main
PCB in the condition open to
atmosphere.
Is the pressure
0MPa displayed on the remote
control?
123 123
- - - -
'19 • PAC-SM-309
Countermeasure
Correct.
NO
Replace low pressure
NO
sensor.
Defective outdoor unit
NO
main PCB ➞ Replace.
Replace low pressure
YES
sensor.