1. Discharge temp. of 100°C or higher was detected 20 minutes or more after that compressor stopped operating.
2. Discharge temp. of 80°C or higher was detected after all compressors had been stopped for 60 minutes or longer.
3. A/D step is 10 steps or less (short circuit).

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 cut or when the connector is not connected to the outdoor unit PCB.
2. Crossed wiring or installation error The discharge temperature sensor of that compressor is connected to the discharge tube of the other compressor. The connector for the discharge temperature sensor of the problem compressor is connected to the outdoor unit PCB connector for the other compressor.
3. Outdoor unit PCB failure
4. The check valve on the discharge tube for that compressor is wet.
5. 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.
6. There is a cause that results in P03, P17, or P02 alarm.
7. Electrical noise

1. Sensor malfunction and outdoor unit PCB failure

  Trouble:

• 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.

   Check:

• 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).
• If the cause is still uncertain, check the following to determine whether a sensor or PCB failure has occurred.
  Step 1: Connect the other compressor discharge sensor, or a discharge sensor where the F04 alarm has not occurred, to the connector for this compressor on the PCB. Measure the temperature at the same point (a location where temperature fluctuations are small), and check whether there is a temperature difference.
  Difference → A PCB or sensor failure is possible.
  No difference → PCB and sensor are normal.
  Step 2: If an abnormality was found at Step 1, connect the problem compressor sensor to the other compressor connector on the PCB, or to the PCB connector of a device where the F04 alarm has not occurred. Measure the temperature at the same point (a location where temperature fluctuations are small), and check whether there is a temperature difference.
  Difference → Sensor failure.
  No difference → PCB failure.
  ☆ It is convenient at this time to have a discharge temperature sensor on hand.

2. Crossed wiring or installation error

  Trouble:

Although the other compressor is operating and this compressor is stopped, the discharge temperature of the other compressor does not increase and the discharge temperature of this compressor rises.
* The discharge temperature remains high immediately after the compressor stops. Wait for some time after the compressor stops and observe.

  Check:

Check for crossed wiring and installation errors.

3. Leakage from the discharge tube check valve

    Trouble:

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.

4. The ambient temperature around the outdoor unit when it is stopped is 43 °C or higher.

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.

1. Replace the sensor.
2. Replace the outdoor unit PCB.
3. Carry out noise countermeasures.
4. Repair the refrigerant tubing.
5. Adjust the amount of refrigerant.
6. Correct the trouble.

1. Sensor wiring is partially cut.