Carrier SUPRA 750Mt - Unit Operates Long or Continuously in Cooling

5
-
4
6
2
-
-
6
1
1
X
X
-
-
2
0
(
0
3
/
0
4
)
I
N
D
I
C
A
T
I
O
N
/
T
R
O
U
B
L
E
P
O
S
S
I
B
L
E
C
A
U
S
E
S
 REFERENCE
SECTION
5.3
.3
Unit
oper
ate
s
long
or
cont
inuou
sly
in
cool
ing
C
o
n
t
a
i
n
e
r
H
o
t
L
o
a
d
Defective box insulation or air leak
Allow time to
pull down
Correct
R
e
f
r
i
g
e
r
a
t
i
o
n
s
y
s
t
e
m
A
b
n
o
r
m
a
l
p
r
e
s
s
u
r
e
Temperature controller malfunction
5.3.6
5.3.8
C
o
m
p
r
e
s
s
o
r
D
e
f
e
c
t
i
v
e
4
.
9
5.3
.4
Unit
will
not
hea
t
or
has
insu
ffi
cie
nt
hea
ting
R
e
f
r
i
g
e
r
a
t
i
o
n
A
b
n
o
r
m
a
l
p
r
e
s
s
u
r
e
Temperature controller malfunction
Hot gas
valve malfunc
tion
5.3.6
5.3.8
5.3.11
C
o
m
p
r
e
s
s
o
r
C
o
m
p
r
e
s
s
o
r
d
r
i
v
e
d
e
f
e
c
t
i
v
e
Compressor defective
4.9
4.9
Engine
does
not d
evelo
p fu
ll rp
m
Speed
control
linkag
e
Engine malfunction
4.3.4
5.1
5.
3.
5
De
fr
ost
cy
cl
e
ma
lf
unc
ti
on
Will not initiate defrost
automatically
Defrost thermostats (DTT) open or defective
Loose terminal connections
Air sensing tubes defective or
discon
nected
Replace
Tighten
Check
Will
not
ini
tiat
e d
efro
st m
anu
all
y
Mic
rop
roc
ess
or d
efe
ctiv
e
Loose terminal connections
Defrost thermostats (DTT) open or defective
Glow/Defro
st
switch defective
Replace
Tighten
Replace
Replace
Ini
tia
tes
bu
t
do
es
no
t
de
fro
st
Ho
t
ga
s
va
lv
e
ma
lfu
nc
tio
n
Defrost relay (DR) defective
5.3.11
Replace
F
r
e
q
u
e
n
t
d
e
f
r
o
s
t
D
e
f
r
o
s
t
t
i
m
e
r
t
o
b
e
a
d
j
u
s
t
e
d
Wet load
2.8.6
Normal
Does not terminate or cycles on
defrost
Defrost thermostats (DTT) shorted closed
Glow/Defro
st
switch defective
Replace
Replace
5.
3.
6
Ab
no
rm
al
pr
es
su
re
5.3.6.
1
Cooling
Hi
gh
d
is
ch
ar
g
e
pr
e
ss
u
re
Co
nd
e
ns
er
co
il
d
ir
ty
Condenser fan defective
V-belt broken or loose
Discharge check valve restricted
Noncondensibles or refrigerant overcharge
4.16.2
Check
4.4
Replace
Replace
Lo
w
di
sc
ha
rg
e
pr
es
su
re
Co
mp
re
ss
or
va
lv
es
(s
)
wo
rn
or
br
ok
en
Hot gas
valve malfunc
tion
4.9
5.3.11
Hi
gh
su
ct
io
n
pr
es
su
re
Co
mp
re
ss
o
r
va
lv
es
(s
)
wo
rn
or
b
ro
ke
n
Compressor gasket(s) defective
Hot gas
valve malfunc
tion
4.9
4.9
2.9.2