Panasonic U-72MF1U9 Service Manual

Also see for U-72MF1U9: Installation instructions Operating instructions Operating instructions Technical data

3 - 9Trouble Diagnosis3. W-3WAY VRF Alarm Codes1234567(3) A/D step is 10 steps or less (short circuit).F04, F05 AlarmAlarm code F04, F05Alarm meaning F04: Compressor 1 discharge temperature sensor (DISCH1) trouble.F05: Compressor 2 discharge temperature sensor (DISCH2) trouble.Alarm conditions (1) Discharge temp. of 212°F or higher was detected 20 minutes or more after thatcompressor stopped operating.stopped for 60 minutes or longer.(2) Discharge temp. of 176°F or higher was detected after all compressors had beenProbable cause (1) Sensor 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 tothe outdoor unit control PCB.(2) Crossed wiring or installation error• The discharge temperature sensor of that compressor is connected to the discharge tubeof the other compressor.• The connector for the discharge temperature sensor of the problem compressor isconnected 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 unitambient temperature, reducing the cooling effects after the compressor stops.(6) There is a cause that results in P03, P17, or P18 alarm.(7) Electrical noise.Check (1) Sensor malfunction and outdoor unit PCB failureTrouble: • Constantly indicates a high temperature.• When monitoring software or other means are used for monitoring, the dischargetemperature at times fluctuates suddenly and wildly.• In some cases, the precise temperature may not be known, even when monitoringsoftware 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 isopen).• If the cause is still uncertain, check the following to determine whether a sensor orPCB failure has occurred.Step 1: Connect the other compressor discharge sensor, or a discharge sensor wherethe F04 alarm has not occurred, to the connector for this compressor on thePCB. Measure the temperature at the same point (a location wheretemperature fluctuations are small), and check whether there is a temperaturedifference.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 compressorsensor to the other compressor connector on the PCB, or to the PCBconnector of a device where the F04 alarm has not occurred. Measure thetemperature at the same point (a location where temperature fluctuations aresmall), and check whether there is a temperature dif ference.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 errorTrouble: Although the other compressor is operating and this compressor is stopped, thedischarge temperature of the other compressor does not increase and the dischargetemperature of this compressor rises.* The discharge temperature remains high immediately after the compressor stops. Waitfor some time after the compressor stops and observe.Check: Check for crossed wiring and installation errors.Continued• Sensor element malfunction→→→→