Chapter 19 Installation and Troubleshooting of Domestic Refrigerators and Freezers
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• Make sure the ice maker thermostat is a single-
throw switch wired in series with the mold heater.
• Make sure the ejector blades make two revolutions
per cycle and that ice is not stored on the blades
after harvest.
• Make sure the water valve solenoid is wired in
series with the mold heater.
19.2.6 Unusual Noises
Audible noises in the refrigerator are caused by
vibrations. The following are common sources of
unusual noises:
• Loose baffles or ducts.
• Tubing touching something that vibrates.
• Listing (leaning to one side) of the condensing unit,
caused by an uneven floor.
• Fan and motor vibration.
• Loose components or panels.
• Loose articles on the shelves.
• Shelves not seated properly on the supports.
An ultrasonic leak detector, like the one shown
in Figure 19-8, can be used to isolate many noises.
(Ultrasonic refers to sound at a frequency above the
human hearing range.) Sounds generated by leaks or
other defects can be located with this tool, which helps
the technician identify and diagnose problems in the
system.
Noise originating from the compressor unit may
indicate that it is laboring too hard. To determine this,
test the electrical load with an ammeter or wattme-
ter. An overloaded compressor unit can sometimes
be identified by its starting behavior. Three seconds
to operate the relay is an average time. A slower start
indicates an overload.
Tubing that rattles against refrigerator parts
should be carefully bent so it no longer contacts those
parts. Be very careful to not kink the tubing as you
bend it. The tubing may be rigid, but may have a vibra-
tion or hum (harmonic vibration). This noise can be
reduced by clamping rubber blocks on the tubing. See
Figure 19-9. Loose baffles and ducts can be secured
with self-tapping sheet metal screws or sealant. Care
should be taken when working on an evaporator to
prevent puncturing the tubing.
19.2.7 Unusual Cycling Times
Cycling time on home refrigerators and freez-
ers cannot be given in definite terms. Cycle times
vary depending on various factors. These include the
amount of storage space inside the cabinet that is being
used, the temperature outside the cabinet, and the
compressor condition.
Placing warm food in the cabinet to be frozen will
also affect the cycling time. In many systems, the com-
pressor runs roughly one-third of the time. In other
words, it may run five minutes and be off ten minutes. It
may run for ten minutes and be off for twenty minutes.
This ratio of on and off time is referred to as the refriger-
ator’s duty cycle. Any unusual or unexpected changes in
cycling time should be investigated immediately. They
may indicate that trouble is developing in the system.
19.2.8 System Failure
The failure may be that the unit is running as nor-
mal, but is not maintaining the proper temperature
Parabola
Sensor horn
Headphone
volume switch
Coarse
sensitivity
switch
Battery power
indicator
On/off switch
and fine
sensitivity
adjustment
LED display
Amprobe
Figure 19-8. An ultrasonic leak detector can be used to
locate the source of leaks and other noises.