Panasonic U-36LE1U6 Service Manual page 31

4. Mini VRF Alarm Codes
F04 alarm
Alarm code F04
Alarm meaning Compressor 1 discharge temperature sensor trouble
Alarm conditions (1) A temperature of 212°F (100°C) or higher was detected 20 minutes or longer after that
compressor stopped running.
(2) Temperature is 176°F (80°C) or higher when the outdoor unit has been stopped for 60 minutes
or longer.
Details are given in the servicing technical materials.
(3) A/D step is 10 steps or less (short circuit).
Probable cause (1) Sensor malfunction
• Sensor element malfunction
• Sensor wiring is partially disconnected, resulting in increased electrical resistance.
This alarm does not occur when the wiring is completely cut or when the connector is not
connected to the outdoor unit PCB.
(2) Outdoor unit PCB failure
(3) An air short blockage in the area around the outdoor unit has increased the outdoor unit
ambient temperature, reducing the cooling effects after the compressor stops.
(4) There is a cause that results in P03 alarm.
(5) Electrical noise
Check (1) Sensor malfunction and outdoor unit PCB failure
Trouble:
Check:
(2) Leakage from the discharge tube check valve
Trouble:
(3) 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.
(1) Replace the sensor.
Correction
(2) Carry out noise countermeasures.
(3) Adjust the amount of refrigerant.
(4) 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.
• Constantly indicates a high temperature.
• When monitoring software or other means are used for monitoring, the discharge
temperature at times fluctuates suddenly and wildly.
• In some cases, the precise temperature may not be known, even when monitoring
software is used.
• Wiggle the sensor and check whether the trouble continues.
• Check whether the connector is partially disconnected from the PCB.
An F04 alarm will not result if the connector is completely disconnected (circuit is
open).
Although the other compressor is operating and this compressor is stopped, the
discharge temperature of this compressor rises together with the temperature of the
other compressor.
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Trouble Diagnosis
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