York YU2E18YJ6AMHO-Y, Service Manual, Page: 78 / 124

78
7.4.2.11 P4 (Temperature protection of compressor discharge) diagnosis and solution.
Error Code P4
Malfunction conditions When the compressor discharge temperature(T5) is more
than 115
℃
for 10 seconds, the compressor will stop
and
restart till T5 is less than 90
℃
.
Potential causes ●
Refrigerant leakage
●
Wiring mistake
●
Faulty discharge temperature sensor
●
Faulty outdoor PCB
Trouble shooting:
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?
Measure 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