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5-2T-309
CONDITION POSSIBLE CAUSE
REMEDY/
REFERENCE
SECTION
5.3 UNIT RUNS BUT HAS INSUFFICIENT COOLING
Abnormal pressures 5.7
Abnormal temperatures 5.15
Abnormal currents 5.16
Controller malfunction 5.9
Evaporator fan or motor defective 6.17
Shortage of refrigerant 6.7.1
Refrigeration System
Suction m odulation valve lost track of step count Power cycle
Suction modulation valve malfunction 6.20
Compressor service valves or liquid line shutoff valve par-
tially closed
Open valves
completely
Economizer solenoid valve or TXV malfunction 6.14, 6.19
Unloader valve stuck open 6.19
Frost on coil 5.10
5.4 UNIT WILL NOT HEAT OR HAS INSUFFICIENT HEATING
Start-Stop switch OFF or defective Check
No operation of any kind
Circuit breaker OFF or defective Check
N
o
o
p
e
r
a
t
i
o
n
o
f
a
n
y
k
i
n
d
External power source OFF Turn ON
Circuit breaker or fuse defective Replace
Control Transformer defective Replace
No control power
Evaporator fan internal motor protector open 6.17
N
o
c
o
n
t
r
o
l
p
o
w
e
r
Heat relay defective C heck
Heater termination thermostat open 6.15
Heater(s) defective 6.15
Heater contactor or coil defective Replace
Evaporator fan motor(s) defective or rotating backwards 6.15/6.17
Unit
w
ill not heat or has insuffi-
Evaporator fan motor contactor defective Replace
U
n
i
t
w
i
l
l
n
o
t
h
e
a
t
o
r
h
a
s
i
n
s
u
f
f
i
-
cient heat
Controller malfunction 5.9
Defective wiring Replace
Loose terminal connections Tighten
Low line voltage 2.3
5.5 UNIT WILL NOT TERMINATE HEATING
Controller improperly set Reset
U
n
i
t
f
a
i
l
s
t
o
s
t
o
p
h
e
a
t
i
n
g
Controller malfunction 5.9
U
n
i
t
f
a
i
l
s
t
o
s
t
o
p
h
e
a
t
i
n
g
Heater termination thermostat remains closed along with
the heat relay
6.15
5.6 UNIT WILL NOT DEFROST PROPERLY
Defrost timer m alfunction (Cd27) Table 3-5
Loose terminal connections Tighten/
Will not initiate defrost
Defective wiring Replace
W
i
l
l
n
o
t
i
n
i
t
i
a
t
e
d
e
f
r
o
s
t
automatically
Defrost temperature sensor defective or heat termination
thermostat open
Replace
Heater contactor or coil defective Replace