COMPONENTS TESTING (Continued)
FAN MOTOR
A single phase permanent split capacitor motor is used to drive the evaporator blower and condenser fan. A
WARNING
ELECTRIC SHOCK HAZARD
Disconnect power to the unit before servicing. Failure to follow this warning could result in serious injury or death.
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.
Figure 23
Blower/Fan Motor
CAPACITORS
WARNING
ELECTRIC SHOCK HAZARD
Turn off electric power before servicing. Discharge capacitor with a 20,000 Ohm 2 Watt resistor before handling.
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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
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
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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
24
