Carrier 40MAQB12B--3 - Compressor Discharge Temperature Protection Error Diagnosis (P4); P4 Compressor Discharge Temperature Troubleshooting

61
P4(Temperature protection of compressor discharge) error diagnosis and
solution.
Error Code P4
Malfunction decision conditions
When the compressor discharge temperature(T5) is more than 239_F for 10 seconds, the
compressor stops and restarts when T5 is less than 194
_F.
Supposed causes
S Refrigerant leakage
S Wiring mistake
S The discharge temperature sensor faulty
S Outdoor PCB faulty
Troubleshooting
T f
c
ompressor disc
h
arge
compressor discharge
C
h
ec
k
w
h
et
h
er t
h
e
compressor disc
h
arge tem
p
.
i
s
m
ore t
h
an
1
15
°
C
?
Check whether the
compressor discharge temp. is
more than 239°F ?
C
heck whether the
connect
i
on
is
r
igh
t
b
etween
compressor
di
sc
h
arg
e
tem
p
.
sensor
a
n
d
PC
B
a
ccor
di
ng
to w
i
r
i
ng
di
agram
s
?
Check whether the
connection is right between
compressor discharge temp.
sensor and PCB according
to wiring diagrams?
M
e
asure t
h
e res
i
stance va
l
ue
of
compressor discharge
tem
p
.
s
ensor
.
I
f the value is
n
ot norma
l
i
s
n
orma
l
re
f
er to
th
e Appen
d
ix
2
?
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 re
f
rigeran
t
Stop leaking and add refrigerant
R
ep
l
ace t
h
e compressor
di
sc
h
arge temp
.
s
ensor
Replace the compressor discharge temp. sensor
No
Yes
R
ep
l
ace
hi
g
h
pressure va
l
ve ass
y
Replace high pressure valve assy
Yes
No
R
e
p
l
ace out
d
oor ma
i
nP
C
B
Replace outdoor main PCB
No
Check whether the
refrigerant is leak
Ch k h h h
g
Check whether the
refrigerant is leak