GSZH5 Service Manual
90
SERVICING
6. If ground is indicated, replace the compressor. The
reading on meter, there is some continuity to ground
and compressor should be considered defective.
Compressor Ground Test
WARNING
Unloader Test Procedure
A nominal 24-volt direct current coil activates the
compressor internal unloader solenoid. The input control
circuit voltage must be 18 to 28 volt ac (remove). The
coil power requirement is 5 VA. The external electrical
connection is made with a molded plug assembly. This plug
unloader coil. The measured DC voltage at the connectors
in the plug should be 15 to 27 volt dc.
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
amperage. Cycle the unloader ON and OFF at 10
second intervals. The compressor amperage should
increase when switching from part-load to full-load
and decrease when switching from full-load to part-
load. The percent change depends on the operating
conditions and voltage, but should be at least 25
percent.
2. If step one does not give the expected results, shut
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.
and remove the control circuit molded plug from the
compressor and measure the unloader coil resistance
(connections on the compressor). The solenoid coil
should have continuity and not be grounded or have
or grounded, the compressor must be replaced.
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 same female connector as before should read
Reverse polarity on the ohmmeter leads and repeat.
should now read close to zero ohms.
Replace plug if either of these test methods doesn’t show
the desired results.
Operation Test
If the voltage, capacitor, overload and motor winding test
fail to show the cause for failure:
WARNING
1. Remove unit wiring from disconnect switch and wire a
test cord to the disconnect switch.
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.