Goodman [A/G]PG, Service Instructions Manual

Page: 38 / 52

SERVICING
38
4. Next check the molded plug.
A. Voltage check: Apply control voltage to the plug wires
(18 to 28 volt ac). The measured
dc voltage at the
female connectors in the plug should be around 15
to 27 vdc.
B. Resistance check: Measure the resistance from the
end of one molded plug lead to either of the two
female connectors in the plug. One of the connec-
tors should read close to zero ohms while the other
should read infinity. Repeat with other wire. The same
female connector as before should read zero while
the other connector again reads infinity. Reverse
polarity on the ohmmeter leads and repeat. The fe-
male connector that read infinity previously should
now read close to zero ohms.
C. Replace plug if either of these test methods doesn’t
show the desired results.
S-17D Operation Test
If the voltage, capacitor, overload and motor winding test fail to
show the cause for failure:
1. Remove unit wiring from disconnect switch and wire a test
cord to the disconnect switch.
NOTE: The wire size of the test cord must equal the line wire
size and the fuse must be of the proper size and type.
2. With the protective terminal cover in place, use the three
leads to the compressor terminals that were disconnected
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 capacitance and volt-
age rating into the circuit.
4. With power ON, close the switch.
Line Voltage now present.
A. If the compressor starts and continues to run, the
cause for failure is somewhere else in the system.
B. If the compressor fails to start - replace.
S-18 TESTING CRANKCASE HEATER
The crankcase heater must be energized a minimum of four
(4) hours before the package unit is operated.
Crankcase heaters are used to prevent migration or accumula-
tion of refrigerant in the compressor crankcase during the off
cycles and prevents liquid slugging or oil pumping on start up.
Scroll Compressors are not equipped with a crankcase heat-
ers.
A crankcase heater will not prevent compressor damage due
to a floodback or over charge condition.
1. Disconnect the heater lead wires.
2. Using an ohmmeter, check heater continuity - should test
continuous, if not, replace.
S-100 REFRIGERATION REPAIR PRACTICE
Always remove the refrigerant charge in a proper
manner before applying heat to the system.
When repairing the refrigeration system:
1. Never open a system that is under vacuum. Air and mois-
ture will be drawn in.
2. Plug or cap all openings.
3. Remove all burrs and clean the brazing surfaces of the
tubing with sand cloth or paper. Brazing materials do not
flow well on oxidized or oily surfaces.
4. Clean the inside of all new tubing to remove oils and pipe
chips.
5. When brazing, sweep the tubing with dry nitrogen to pre-
vent the formation of oxides on the inside surfaces.
6. Complete any repair by replacing the liquid line drier in the
system, evacuate and charge.
At any time the system has been open for repair, the factory
installed liquid line filter drier
must be replaced.
BRAZING MATERIALS
Copper to Copper Joints - Sil-Fos used without flux (alloy of
15% silver, 80% copper, and 5% phosphorous). Recommended
heat 1400°F.
Copper to Steel Joints - Silver Solder used without a flux
(alloy of 30% silver, 38% copper, 32% zinc). Recommended
heat - 1200°F.