Panasonic U-72MF2U9 Service Manual page 172

3. 3WAY Alarm Codes
F04, F05 Alarm
Alarm code
Alarm meaning
Alarm conditions
Probable cause
1
2
3
Check
4
5
6
7
8
9
F04, F05
F04 : DISCH1 thermistor at the discharge of 1st compressor reading is abnormal.
F05 : DISCH2 thermistor at the discharge of 2nd compressor reading is abnormal.
(1) Discharge temp. of 212°F (100°C) or higher was detected 30 minutes or more after that
compressor stopped operating.
(2) Discharge temp. of 176°F (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 disconnected or when the connector is not
connected to the Outdoor Unit Control 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 Control PCB connector for the other compressor.
(3) Outdoor Unit Control 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 or P17 alarm.
(7) Electrical noise
(1) Sensor malfunction and Outdoor Unit Control 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 Outdoor Unit Control
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
Outdoor Unit Control 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
Outdoor Unit Control PCB. Measure the temperature at the same point (a
location where temperature fluctuations are small), and check whether there is a
temperature difference.
Difference →
No difference → Outdoor Unit Control 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 Outdoor Unit Control PCB, or
to the 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 →
No difference → Outdoor Unit Control 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.
Outdoor Unit Control PCB or sensor failure is possible.
Sensor failure.
5 - 10
3WAY VRF SYSTEM
Trouble Diagnosis
Continued