Panasonic U-100PEY1E5, Technical Data & Service Manual, Page: 656 / 739

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5
L18 4-way Valve Operation Failure
Error Detection Method
Error Diagnosis
It is judged an error when during heating operation (Comp. ON), the highest detected temperature at an outdoor unit
heat exchanger (C1) was 20°C or more above the outdoor air temperature (Air Temp.) continuously for 5 minutes or
longer.
1.
2.
Is the connector wired from the 4-WAY valve plugged in the CN-20S
connector on the HIC PC board properly?
1-1
1-2
Correct connector
Yes
No
2
Has the 4-way valve wiring become opened? 1-2
Is the wire from the coil for controlling the 4-way valve firmly
connected to the 4-way valve?
1-3
4-way valve
1 PC board
wiring
Correct wiring
1-3
Yes
No
2-1
Correct connector
Yes
No
During heating mode (Comp. ON), insert and remove the connector
wired from the 4-WAY valve into or from CN-20S connector on the
HIC PC board. At the same time, does the ON & OFF sounds occur
from the 4-way valve?
2-1
2-2
Replace HIC
PC board
Yes
No
During heating mode (Comp. ON), does the alarm code L18
reproduce for 5 minutes or longer after insertion and removal of
CN-20S connector wired from the 4-way valve connector on the
HIC PC board?
2-2
The parts inside the 4-way valve might have fixed at the cooling side.
Replace the 4-way valve
2-3
2-3
See what happens
Yes
No
SM830211-07̲PAC-i.indb 48 SM830211-07̲PAC-i.indb 48 2013/09/07 10:42:30 2013/09/07 10:42:30