Troubleshooting MLCAC-UTSM-2010-10
108 Outdoor Units
10.3.2.14. P4 malfunction
When compressor discharge temperature is higher than 115°C, the unit will stop, and unit runs again when
compressor discharge temperature is lower than 90°C.
P4 display
Temperature protection of
compressor discharge
Check whether the
compressor discharge temp.
is more than 115°C ?
Check whether the wiring
connection is right between
compressor discharge temp.
sensor and PCB according
to wiring diagrams?
Method: Check whether the
resistance of compressor
discharge temp. sensor is
right refer to the Appendix 2
No
Yes
Yes
Trouble is solved
No
Judge: The
discharge temp.
sensor is broken
Check whether the
refrigerant is leak
Correct the wiring connection
Stop leaking and add refrigerant
Replace the compressor discharge temp. sensor
No
Yes
Replace outdoor main board
Yes
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