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SERVICING
50
Do not use a low voltage output instrument such as a volt-
ohmmeter.
HI-POT
COMPRESSOR GROUND TEST
3. If a ground is indicated, then carefully remove the com-
pressor terminal protective cover and inspect for loose
leads or insulation breaks in the lead wires.
4. If no visual problems indicated, carefully remove the
leads at the compressor terminals.
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.
Carefully retest for ground, directly between compressor
terminals and ground.
5. If ground is indicated, replace the compressor.
S-17C UNLOADER TEST PROCEDURE
A nominal 24-volt direct current coil activates the internal
unloader solenoid. The input control circuit voltage must be
18 to 28 volt ac. The coil power requirement is 20 VA. The
external electrical connection is made with a molded plug
assembly. This plug contains a full wave rectifier to supply
direct current to the unloader coil.
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 compressor 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 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 infin-
ity. 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-17D OPERATION 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 discon-
nected at the nearest point to the compressor and
connect the common, start and run clips to the respec-
tive leads.