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138
TK 61555-2-MM-EN
Rapid
cycling
between
cool
and
heat
Unit
cools
in
heat
and
defrost
cycle
Unit
heats
in
refrigeration
cycle
High
head
pressure
Low
head
pressure
High
suction
pressure
Low
suction
pressure
No
suction
pressure
Unit
operating
in
a
vacuum
Receiver
sight
glass
empty
Suction
line
frosting
back
Unable
to
pump
down
system
Unable
to
pull
vacuum
in
low
side
Unable
to
hold
vacuum
in
low
side
Noisy
compressor
Unit
not
refrigerating
Unit
not
heating
or
defrosting
SYMPTOM
POSSIBLE CAUSES
•
•
Restricted line on the low side
•
•
•
•
Restricted line on the high side
•
•
•
•
Restricted drier
•
Defrost damper stays open
•
•
•
Defrost damper stuck closed
•
Evaporator fans stay running
•
•
•
Evaporator fans not running
•
Suction service valve back seated
•
•
•
•
•
•
•
•
Faulty three-way valve
•
•
•
•
•
Faulty pilot solenoid
•
•
Loose or broken electrical connections
•
•
•
•
•
Sensor out of calibration
•
•
•
•
Compound pressure gauge out of calibration
•
Leaky receiver tank outlet valve
•
Leaky bypass check valve
•
Leaky condenser check valve
•
Faulty three-way condenser pressure bypass check
valve