Service Manual

SERVICING
29
WARNING
DAMAGE CAN OCCUR TO THE GLASS EMBEDDED
TERMINALS IF THE LEADS ARE NOT PROPERLY
REMOVED. THIS CAN RESULT IN TERMINAL AND
HOT OIL DISCHARGING.
HI-POT
COM PRESSOR GROUND TEST
2. Identify the leads and using a M egger, Hi-Potent ial Ground
Tester, or other suit able inst rument which put s out a volt-
age between 300 and 1500 volts, check for a ground sepa-
rat ely betw een each of the three leads and ground (such as
an unpaint ed t ube on the compressor). Do not use a low
volt age output inst rument such as a volt-ohmmet er.
3. If a ground is indicated, then carefully remove the compres-
sor terminal protective cover and inspect for loose leads or
insulation breaks in t he lead wires.
4. If no visual problems indicated, carefully remove the leads at
the compressor terminals.
Carefully retest for ground, directly bet ween compressor ter-
minals and ground.
5. If ground is indicat ed, replace the compressor.
S-17D OPERATION TEST
If the voltage, capacit or, overload and mot or winding test fail to
show the cause for failure:
WARNING
1. Remove unit wiring from disconnect sw itch and wire a test
cord to the disconnect sw it ch.
NOTE: The wire size of the t est cord must equal the line wire size
and the fuse must be of the proper size and type.
2. With the prot ect ive terminal cover in place, use the three leads
to t he compressor terminals that were disconnect ed at the
nearest point to the compressor and connect the common,
start and run clips to the respective leads.
3. Connect good capacitors of the right M FD and voltage rat ing
into the circuit.
4. With power ON, close t he switch.
WARNING
LINE VOLTAGE NOW PRESENT.
A. If t he compressor st art s and cont inues t o run, the
cause for failure is somewhere else in the syst em.
B. If the compressor fails to st art - replace.
The condition of the scroll flanks is checked in the following
manner.
1. Attach gauges to the high and low side of the syst em.
2. Start the system and run a “ Cooling Performance Test.
If the test shows:
a.
Below normal high side pressure.
b.
Above normal low side pressure.
c. Low temperature difference across coil.
d.
Low amp draw at compressor.
and the charge is correct, test the reversing valve if equipped
(heat pump models only. See-S-21). If the reversing valves
test good, the compressor is faulty - replace the compressor.
S-18 TESTING CRANKCASE HEATER
(OPTIONAL ITEM )
Note: Not all compressors use crankcase heaters.
The crankcase heat er must be energized a minimum of twent y-
four (24) hours before the compressor is operat ed.
Crankcase heaters are used to prevent migrat ion or accumula-
tion of refrigerant in t he compressor crankcase during the off
cycles and prevent s liquid slugging or oil pumping on start up.
On some models, t he crankcase heater is controlled by a crank-
case heater thermostat that is wired in series wit h the crankcase
heat er.
A crankcase heater will not prevent compressor damage due to
a floodback or over charge condition.