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17.4.21 H99 (Indoor Unit Heat Exchanger Freezing Protection (Error Code is to be Stored in
the Memory only))
Troubleshooting
Diagnosis Procedures and Cause
Measures to be Taken
For some models, the sensor is not connected by a connector but
it is directly soldered to the board.
In this case, replace the control board.
There is a gas leak
No abnormality is observed
No abnormality is observed
No abnormality is observed
An abnormality
is observed
Normal
There is no
gas leak
Filter is clogged
Check for clogged filter on the indoor unit.
Check for the characteristics of the indoor unit heat exchanger temperature sensor.
Refer to the characteristic table for electronic circuit diagram.
(Remove the connector and check the resistance value of the sensor.)
Check the gas pressure during the rated cooling operation.
Check for presence of gas leak.
Clean the filter.
Replace the indoor unit heat
exchanger temperature sensor.
Replace the part from which gas is
leaking.
Replace the indoor unit control board.
Replace the capillary tube or
expansion valve.
Rotation is slow
Is the rotation of the indoor unit fan motor slow?
Replace the indoor unit fan motor.
Disconnection/
Imperfect
connection of
the connector
Check for bad connection of the connector of the indoor unit pipe temperature
sensor.
Fix the problem.
No abnormality
is observed
Lower than the standard value
Not frozen
Check for frozen indoor unit heat exchanger.
Frozen
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