Chapter 19 Installation and Troubleshooting of Domestic Refrigerators and Freezers
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of the refrigerator to help feed the wires. Seal the hole
with silicone sealant after the wire or wires are pulled
through.
If the cabinet temperature is not responding prop-
erly to the thermostat, the thermostat may be faulty.
A set of alligator clips can be used to jump across the
terminals of the thermostat, bypassing it. If the com-
pressor starts with the thermostat bypassed, the prob-
lem is in the thermostat. If the compressor fails to start
with the thermostat bypassed, the problem is else-
where in the circuit.
If the thermostat will not start the compres-
sor when the cut-in temperature is reached, or keeps
the system running after the cut-out temperature is
reached, it should be replaced. If there is time for a
return service call the next day, use a data logger to
record the cabinet temperature over a 24-hour period.
The recorded data will show if the appliance is operat-
ing properly.
19.4 Diagnosing Internal Troubles
Once you have eliminated external problems as
the cause of failure, it is time to troubleshoot the refrig-
eration system itself. There are many ways to find the
cause of trouble inside a small hermetic system. This
is done using gauges, thermometers, and electrical
instruments, combined with careful observation. A
properly trained service technician should be able to
locate the cause of any problem in a system.
The evaporator may be partially frosted. This indi-
cates that not enough refrigerant is flowing through
the metering device into the evaporator. As a result, the
refrigerant that does enter the evaporator is completely
vaporized after passing only partway through it. This
lowers the system’s cooling capacity and efficiency.
This can be caused by a low refrigerant charge or by a
partially clogged metering device.
A low refrigerant charge results from a leak in the
system. Leaks on new refrigeration units can be the
result of manufacturing defects or broken or cracked
lines from shipping or installation. Older units may
develop leaks as a result of vibration of the tubing,
which can cause cracks at the tubing joints.
If liquid refrigerant makes it all the way through
the evaporator and into the suction line before vapor-
izing, frost or sweat may form on the suction line. In
a capillary tube system, this can be caused by a bro-
ken thermostat or an overcharge of refrigerant. Either
of these conditions results in more refrigerant entering
Fuse
Start switch
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Start capacitor
Run capacitor
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A. W Sperry Instruments, Inc.
Figure 19-13. Test cord arrangement for a capacitor-start, capacitor-run hermetic motor. Clip 1 is connected to the common winding
terminal. Clip 2 is connected to the run winding terminal. Clip 3 is attached to the start winding terminal. Clip 4 is attached to the
ground.
Switch
Fuse
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3
A. W. Sperry Instruments, Inc.
Figure 19-14. A test cord like the one shown here can be used to test a fan motor. Clip 1 is attached to the common winding terminal.
Clip 2 is attached to the power winding terminal. Clip 3 is attached to the ground.