North American HVAC MOC-12HFN1-MS0W, Service Manual

Page: 146 / 157

Troubleshooting
142 Electrical Control System
2.4.4.13. 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
connection is right between
compressor discharge temp.
sensor and PCB according
to wiring diagrams?
M easure the resistance value
of
compressor discharge
temp. sensor .
If the value is
not normal
is normal refer to
the Appendix 2?
No
Yes
Yes
No Correct the wiring connection
Stop leaking and add refrigerant
Replace the compressor discharge temp. sensor No
Yes
Replace high pressure valve assy
Yes
No
Replace outdoor main PCB
No
Check whether the
refrigerant is leak