Panasonic U-4LE1E5 Service Manual page 118

3. Mini VRF System Alarm Codes
L18 4-way valve operation failure
1. Error Detection Method
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, or the detected suction temperature (SCT) was 20°C or more above the outdoor air temperature continuously
for 5 minutes or longer.
2. Error Diagnosis
1 PC board
1-1
wiring
1-2
1-3
4-way valve
2
2-1
2-2
2-3
5
Is the connector wired from the 4-WAY valve plugged in the CN-20S
connector on the HIC PC board properly?
Has the 4-way valve wiring become opened?
Is the wire from the coil for controlling the 4-way valve firmly
connected to the 4-way valve?
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?
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 ?
The parts inside the 4-way valve might have fixed at the cooling side.
Replace the 4-way valve
5 - 38
Mini VRF SYSTEM
Trouble Diagnosis
Yes 1-2
No Correct connector
Yes Correct wiring
No 1-3
Yes 2-1
No Correct connector
Yes 2-2
Replace HIC
No
PC board
Yes 2-3
No See what happens