Service manual

SERVICING
30
RELAY, START
A potential or voltage type relay is used to take the start
capacitor out of the circuit once the motor comes up to
speed. This type of relay is position sensitive. The nor-
mally closed contacts are wired in series with the start ca-
pacitor and the relay holding coil is wired parallel with the
start winding. As the motor starts and comes up to speed,
the increase in voltage across the start winding will ener-
gize the start relay holding coil and open the contacts to
the start capacitor.
Two quick ways to test a capacitor are a resistance and a
capacitance check.
S-15A Resistance Check
WARNING
Disconnect Electrical Power Supply:
1. Discharge capacitor and remove wire leads.
WARNING
DISCHARGE CAPACITOR THROUGH A 20 TO 30 OHM
RESISTER BEFORE HANDLING.
Capacitor
Volt / Ohm
Meter
TESTING CAPACITOR RESISTANCE
2. Set an ohmmeter on its highest ohm scale and connect
the leads to the capacitor -
A. Good Condition - indicator swings to zero and slowly
returns to infinity. (Start capacitor will bleed resistor will
not return to infinity. It will still read the resistance of
the resistor).
B. Shorted - indicator swings to zero and stops there -
replace.
C. Open - no reading - replace. (Start capacitor would
read resistor resistance).
S-15B Capacitance Check
Using a hookup as shown below, take the amperage and
voltage readings and use them in the formula:
WARNING
DISCHARGE CAPACITOR THROUGH A 20 TO 30 OHM
RESISTOR BEFORE HANDLING.
Capacitance (MFD) = 2650 X Amperage
Voltage
15 AMP FUSE
Volt / Ohm
Meter
AMMETER
Capacitor
TESTING CAPACITANCE
S-16 CHECKING FAN AND BLOWER MOTOR
An auto reset fan motor overload is designed to protect the
motor against high temperature and high amperage condi-
tions similar to the compressor internal overload. It also
breaks the common circuit within the motor shell; however,
heat generated within the motor is faster to dissipate than
the compressor, allow at least 45 minutes for the overload
to reset, then retest.
WARNING
Disconnect Electrical Power Supply:
1. Remove the motor leads from its respective connection
points and capacitor (if applicable).
2. Check the continuity between each of the motor leads.
3. Touch one probe of the ohmmeter to the motor frame
(ground) and the other probe in turn to each lead.
If the windings do not test continuous or a reading is ob-
tained from lead to ground, replace the motor.
S-17 CHECKING COMPRESSOR WINDINGS
WARNING
HERMETIC COMPRESSOR ELECTRICAL TERMINAL
VENTING CAN BE DANGEROUS. WHEN INSULATING
MATERIAL WHICH SUPPORTS A HERMETIC COM-
PRESSOR ELECTRICAL TERMINAL SUDDENLY DISIN-
TEGRATES DUE TO PHYSICAL ABUSE OR AS A RE-
SULT OF AN ELECTRICAL SHORT BETWEEN THE TER-
MINAL AND THE COMPRESSOR HOUSING, THE TER-
MINAL MAY BE EXPELLED, VENTING THE VAPOROUS
AND LIQUID CONTENTS OF THE COMPRESSOR HOUS-
ING AND SYSTEM.