GSZ16 Service Manual

SERVICING
98
UNLOADER SOLENOID
(Molded Plug)
Unloader Test Procedure
If it is suspected that the unloader is not working, the following
methods may be used to verify operation.
1. Operate the system and measure compressor current. Cycle
the unloader ON and OFF at 10 second intervals. The com-
pressor amperage should go up or down at least 25 percent.
2. If step one does not give the expected results, shut unit off.
Apply 18 to 28 volt ac to the unloader molded plug leads and
listen for a click as the solenoid pulls in. Remove power and
listen for another click as the unloader returns to its original
position.
3. If clicks can’t be heard, shut off power and remove the control
circuit molded plug from the compressor and measure the
unloader coil resistance. The resistance should be 32 to 60
ohms, depending on compressor temperature.
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 connectors 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 female 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-17DOPERATION TEST
If the voltage, capacitor, overload and motor winding test fail to
show the cause for failure:
HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing. Multiple power sources
may be present. Failure to do so may
cause property damage, personal injury
or death.
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 MFD and voltage rating
into the circuit as shown.
4. With power ON, close the switch.
WARNING
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.
COPELAND COMPRESSOR
03 A 12345 L
Y
EAR
MONTH
SERIAL
NUMBER
PLANT
S-17E CHECKING 3-PHASE SCROLL COMPRESSOR
ROTATION
Verify the proper rotation of Copeland scroll compressors as
follows:
NOTE: The compressor may run backwards (noisy operation)
for 1 or 2 seconds at shutdown. This is normal and does not
harm the compressor.
1. Install gauges and verify that the suction pressure drops
while the discharge pressure increases.
2. Listen for normal compressor sound levels. Reverse rotation
results in elevated or unusual sound levels.
3. Reverse rotation will result in substantially reduced amp
draw from tabulated values.
To correct improper rotation, switch any two power supply leads
at the outdoor unit contactor.