Panasonic U-8MF2E8 Service Manual page 145

4. 3WAY Alarm Codes
P04 Alarm
Alarm code P04
Alarm meaning High-pressure switch activated.
Alarm conditions The operation of the electronic circuit in the high-pressure switch may short-circuit the terminal
depending on the pressure. A pressure of 3.8 MPa or above will short-circuit the terminal. Once
the terminal is short-circuited, it will remain in that state until the pressure goes below 3.15 MPa.
Probable cause (1) High-pressure switch failure or wiring connection failure
(2) Failure to open the service valve of the outdoor unit
(3) Difference of characteristics of high-pressure sensor
(4) Clogging of the outdoor heat exchanger during cooling
(5) Air short circuit occurs during cooling.
(6) Failure of the outdoor fan during cooling
(7) Clogging of the air filter in the indoor unit during heating
(8) Air short circuit occurs during heating.
(9) Failure of the indoor fan during heating
(10) Clogging of the refrigerant circuit
(11) Failure of the expansion valve
(12) Failure of the solenoid valve kit
(13) Too much refrigerant has been charged.
(14) The wiring from the solenoid valve kit is actually connected to the different indoor unit.
(15) The system is that the multiple indoor units are connected at only one solenoid valve kit and also
multiple remote controllers are connected. "Installation of the common use solenoid valve kit"
from a PC has not been made.
Check (1) High-pressure switch failure or wiring connection failure
• Check under the section 6. "Inspection of Parts (1) High-pressure switch".
• Check whether the socket of the high-pressure switch is surely inserted into the outdoor unit PCB.
(2) Failure to open the service valve of the outdoor unit.
• Check open/closed status of the outdoor unit service valve.
(3) Difference of characteristics of high-pressure sensor
• Connect a gauge to the high-pressure outlet and check for changes in the value dispalyed by the
monitoring software, and for large deviation of the gauge pressure.
(4) During cooling, check whether the outdoor unit heat exchanger is clogged. Remove any foreign
material that prevents ventilation.
(5) During cooling, check whether an air short blockage has occurred in the outdoor unit. The system is
operating normally unless the temperature around the outdoor unit is excessively high.
(6) During cooling, check for outdoor fan failure. Check whether the screws securing the fan are loose
and whether the fan connector in the outdoor unit PCB is properly connected.
(7) During heating, check whether the air filters in the indoor unit are clogged. If clogged, clean the
filters.
(8) During heating, check whether an air short blockage has occurred in the indoor unit. The system
operates normally unless the temperature around the indoor unit is excessively high.
(9) During heating, check for indoor fan failure.
(10) Check whether the refrigerant circuit is clogged. Check that all service valves are closed.
Check whether welded locations are clogged.
(11) Check for expansion valve failure. Check whether the expansion valves make a clattering sound
when the power is reset. Since the expansion valve in the indoor unit is in a location that makes
aural inspection difficult, use an electric means to check. Check that the connector pin of the
expansion valve on the PCB outputs 4 V. In addition, check that the coil resistance of the
expansion valve is several tens of Ohm (
(12) Check for solenoid valve kit failure. Removing a coil that is on will result in a clicking sound.
Also, removing a coil that is off will not produce such a sound.
(13) Check whether too much refrigerant has been charged. Too much refrigerant has been
charged if the sub-cool temperature of the condenser is 15°C or more.
(14) Check whether the wiring from the solenoid valve kit is actually connected to the different indoor
unit .
(15) The system is that the multiple indoor units are connected at only one solenoid valve kit and also
multiple remote controllers are connected. Check whether "installation of the common use solenoid
valve kit" from a PC has been made. (Confirmation from the address setting software of a PC)
Correction Replace damaged components and correct the amount of charged refrigerant.
P05 Alarm
Alarm code P05
Alarm meaning Reverse phase (or missing phase) detected
Alarm conditions This alarm occurs when a reverse phase or missing phase is detected in the L1-L2-L3 phases.
Probable cause Reverse phase or missing phase in the L1-L2-L3 phases
Check Check the wiring at the power terminal board.
Correction Switch the phases and reinsert. Check if the result is OK.
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3WAY SYSTEM
Trouble Diagnosis
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