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The overload is wired in series with the common motor
terminal. The overload senses both major amperage and
compressor temperature. High motor temperature or
amperage heats the disc causing it to open and break
the circuit to the common motor terminal.
Figure 3: External Overload
Heat generated within the compressor shell is usually
due to:
1. High amperage.
2. Low refrigerant charge.
3. Frequent recycling.
4. Dirty condenser.
THERMAL OVERLOAD - TEST
(Compressor - External Type)
1. Remove overload.
2. Allow time for overload to reset before attempting
to test.
3. Apply ohmmeter probes to terminals on overload
wires. There should be continuity through the over-
load.
TERMINAL OVERLOAD (Internal)
Some model compressors are equipped with an inter-
nal overload. The overload is embedded in the motor
windings to sense the winding temperature and/or cur-
rent draw. The overload is connected in series with the
common motor terminal.
Should the internal temperature and/or current draw be-
come excessive, the contacts in the overload will open,
turning off the compressor. The overload will automati-
cally reset, but may require several hours before the heat
is dissipated.
CHECKING THE INTERNAL OVERLOAD
(see Figure 4.)
Figure 4
1. With no power to unit, remove the leads from the
compressor terminals.
2. Using an ohmmeter, test continuity between ter-
minals C-S and C-R. If not continuous, the com-
pressor overload is open and the compressor must
be replaced.
FAN MOTOR
A single phase permanent split capacitor motor is used
to drive the evaporator blower and condenser fan.
A self-resetting overload is located inside the mo-
tor to protect against high temperature and high
amperage conditions.
FAN MOTOR - TEST
1. Determine that capacitor is serviceable.
2. Disconnect fan motor wires from fan speed switch
or system switch.
3. Apply “live” test cord probes on black wire and com-
mon terminal of capacitor. Motor should run at high
speed.
4. Apply “live” test cord probes on red wire and com-
mon terminal of capacitor. Motor should run at low
speed.