Part
6
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Diagnosis and Troubleshooting
ODU stop valves are closed
High pressure sensor connection on
outdoor main PCB is loose
1
Ensure the sensor is connected properly
High pressure sensor has short-circuited
or failed
2
Discharge part of the refrigerant. Add oil
if it leaks during discharge
System contains air or nitrogen
4
Flush all refrigerant then vacuum the
system and recharge the refrigerant. Add
oil to the system if it leaks
The high pressure side is blocked, caused
by crushed or bent pipe or blocked EEV
5
Inspect the system and fix the error
The condenser heat exchange is poor
6
Inspect the system and fix the error
Replace the outdoor main PCB
Notes:
1. The high pressure sensor connection is port CN17 on the outdoor main PCB.
2. Measure the resistance among the three terminals of the pressure sensor. If the resistance is of the order of mega Ohms or infinite, the pressure sensor has
failed.
3. Excess refrigerant causes discharge temperature to be lower than normal, discharge pressure to be higher than normal and suction pressure to be higher
than normal.
4. Air or nitrogen in the system causes discharge temperature to be higher than normal, discharge pressure to be higher than normal, compressor current to
be higher than normal, abnormal compressor noise and an unsteady pressure meter reading.
5. High pressure side blockage causes discharge temperature to be higher than normal, discharge pressure to be higher than normal and suction pressure to
be lower than normal.
6. In cooling mode check outdoor heat exchangers, fans and air outlets for dirt/blockages. In heating mode check indoor heat exchangers, fans and air outlets
for dirt/blockages.
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