38
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. 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 common terminal of capacitor. Motor should run at high speed.
4. Apply “live” test cord probes on red wire and common terminal of capacitor. Motor should run at low speed.
5. Apply “live” test cord probes on each of the remaining wires from the speed switch or system switch to test intermediate
speeds. If the control is in the “MoneySaver” mode and the thermostat calls for cooling, the fan will start - then stop after
approximately 2 minutes; then the fan and compressor will start together approximately 2 minutes later.
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 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 identified terminal is connected to the “S” or start terminal. The identified 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 706 (Blower)
Figure 707 Dual Rated Capacitor Hook-Up
