30 PB
COMPONENTS TESTING
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.
WARNING
ELECTRIC SHOCK HAZARD
Turn off electric power before service or
installation. Extreme care must be used, if it
becomes necessary to work on equipment with
power applied.
Failure to do so could result in serious injury or
death.
Figure 23
Blower/Fan Motor
Blower / Fan Motor Test
1. Check Capacitor as shown below.
2. Place the unit into fan only mode, and verify proper voltage at motor leads.
3. If proper voltage exists, check the resistance of the windings, replace fan motor.
Capacitors
WARNING
ELECTRIC SHOCK HAZARD
Turn off electric power before service or
installation. Extreme care must be used, if it
becomes necessary to work on equipment with
power applied.
Failure to do so could result in serious injury or
death.
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.
Capacitor Check
The meter 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 common terminal is connected to the “S” or start terminal. The common 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.
Dual Rated Run Capacitor Hook-up
Figure 503 (Blower)
Figure 504 Dual Rated Capacitor Hook-Up
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