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Section 2 - Troubleshooting
REFRIGERATION SYSTEM DIAGNOSIS GUIDE
THERMISTOR TYPES
Type 1 (Black)
Resistance at 77°F = 10,000 Ohms ± 5%.
Operating range is 185,000 to 650 Ohms. Resistance goes
down as temperature increases. Type 1 does not need to be
calibrated and can be changed without changing other wires
or board.
Type 2 (White)
Resistance at 77°F = 5,000 Ohms ± 5%.
Operating range is 180,000 to 550 Ohms. Resistance goes
down as temperature increases. Type 2 does not need to be
calibrated and can be changed without changing other wires
or board.
System
Condition
Suction
Pressure
Suction
Line
Compressor
Discharge
Condenser Capillary
Tube
Evaporator Wattage
Normal Normal Slightly below
room
temperature
Very hot Very hot Warm Cold Normal
Overcharge Higher than
normal
Very cold may
frost heavily
Slightly warm
to hot
Hot to warm Cool Cold Higher than
normal
Undercharge Lower than
normal
Warm-near
room
temperature
Hot Warm Warm Extremely
cold near
inlet - Outlet
below room
temperature
Lower than
normal
Partial
Restriction
Somewhat
lower than
normal
vacuum
Warm - near
room
temperature
Very hot Top passes
warm - Lower
passes cool
(near room
temperature)
due to liquid
Room
temperature
(cool) or
colder
Extremely
cold near
inlet - Outlet
below room
temperature
backing up
Lower than
normal
Complete
Restriction
In deep
vacuum
Room
temperature
(cool)
Room
temperature
(cool)
Room
temperature
(cool)
Room
temperature
(cool)
No
refrigeration
Lower than
normal
No Gas 0 PSIG to 25” Room
temperature
(cool)
Cool to hot Room
temperature
(cool)
Room
temperature
(cool)
No
refrigeration
Lower than
normal