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BLOWER / FAN MOTOR TEST
BLOWER / 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 motor to protect against high
temperature and high amperage conditions.
ELECTRIC SHOCK HAZARD
WARNING
Disconnect power to the unit before
servicing. Failure to follow this warning
could result in serious injury or death.
1. Visually inspect the motor’s wiring, housing etc., and
determine that the capacitor is serviceable.
2. Make sure the motor has cooled down.
3. Disconnect the fan motor wires from the control board.
4. Test for continuity between the windings also, test to
ground.
5. If any winding is open or grounded replace the motor.
CAPACITORS
ELECTRIC SHOCK HAZARD
WARNING
Turn off electric power before servicing.
Discharge capacitor with a 20,000 Ohm 2 Watt
resistor before handling.
Failure to do so may result in personal injury,
or death.
Capacitor Check with Capacitor Analyzer
The capacitor analyzer will show whether the capacitor
is “open” or “shorted.” It will tell whether the capacitor
is within its micro farads rating and it will show whether
the capacitor is operating at the proper power-factor
percentage. The instrument will automatically discharge
the capacitor when the test switch is released.
Capacitor Connections
The starting winding of a motor can be damaged by a
shorted and grounded running capacitor. This damage
usually can be avoided by proper connection of the running
capacitor terminals.
From the supply line on a typical 230 volt circuit, a 115 volt
potential exists from the “R” terminal to ground through a
possible short in the capacitor. However, from the “S” or start
terminal, a much higher potential, possibly as high as 400
volts, exists because of the counter EMF generated in the
start winding. Therefore, the possibility of capacitor failure
is much greater when the identied terminal is connected
to the “S” or start terminal. The identied terminal should
always be connected to the supply line, or “R” terminal,
never to the “S” terminal.
When connected properly, a shorted or grounded running
capacitor will result in a direct short to ground from the “R”
terminal and will blow the line fuse. The motor protector
will protect the main winding from excessive temperature.
COMPONENTS TESTING
Many motor capacitors are internally fused. Shorting the
terminals will blow the fuse, ruining the capacitor. A 20,000
ohm 2 watt resistor can be used to discharge capacitors
safely. Remove wires from capacitor and place resistor
across terminals. When checking a dual capacitor with
a capacitor analyzer or ohmmeter, both sides must be
tested.
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