Panasonic U-72MF2U9 Service Manual page 173

3. 3WAY Alarm Codes
Check (3) Leakage from the discharge tube check valve
Trouble: Although the other compressor is operating and this compressor is stopped, the
(4) The ambient temperature around the outdoor unit when it is stopped is over an operating
temperature range.
(5) If the cause is still unknown after checking the above, then it is possible that electrical noise is
the cause of the trouble. It is necessary to provide a line filter or carry out other noise
countermeasures.
F05 (2nd compressor) is also the same.
Correction (1) Replace the sensor.
(2) Replace the Outdoor Unit Control PCB.
(3) Carry out noise countermeasures.
(4) Repair the refrigerant tubing.
(5) Adjust the amount of refrigerant.
(6) Correct the trouble.
Example (1) Sensor wiring is partially cut.
Notes This alarm does not indicate that the sensor is disconnected.
In order to prevent overheating during operation, the outdoor units in this system will not allow a
compressor to start if the discharge temperature does not decrease while the compressor is
stopped. If a sensor malfunction results in continuous detection of a high discharge temperature,
then the compressor may stop for no apparent reason. The purpose of this alarm is to facilitate
identification of the problem in this case.
F06, F23 Alarm
Alarm code F06, F23
Alarm meaning F06 : EXG1 thermistor at the gas side of 1st heat exchanger of the outdoor unit has failure. (EXG1)
F23 : EXG2 thermistor at the gas side of 2nd heat exchanger of the outdoor unit has failure. (EXG2)
Alarm conditions (1) Short circuit (A/D step is 10 steps or less.)
(2) Open circuit (A/D step is 1014 steps or more.)
Probable cause (1) Sensor malfunction (including connector)
(2) The Outdoor Unit Control PCB malfunction
Check (1) Measure the sensor resistance. Check that the sensor is operating normally.
(2) Use a remote controller monitor or PC monitor to check the temperature that is recognized by
the microcomputer.
Correction —
Example —
Notes —
F07, F24 Alarm
Alarm code F07, F24
Alarm meaning F07 : EXL1 thermistor at the liquid side of 1st heat exchanger of the outdoor unit has failure. (EXL1)
F24 : EXL2 thermistor at the liquid side of 2nd heat exchanger of the outdoor unit has failure. (EXL2)
Alarm conditions (1) Short circuit (A/D step is 10 steps or less.)
(2) Open circuit (A/D step is 1014 steps or more.)
Probable cause (1) Sensor malfunction (including connector)
(2) The Outdoor Unit Control PCB malfunction
Check (1) Measure the sensor resistance. Check that the sensor is operating normally.
(2) Use a remote controller monitor or PC monitor to check the temperature that is recognized by
the microcomputer.
Correction —
Example —
Notes —
discharge temperature of this compressor rises together with the temperature of the
other compressor.
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3WAY VRF SYSTEM
Trouble Diagnosis
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