Defrost Heater; Defrost Terminator - Viking VCFB5301 Service Manual

To avoid risk of electrical shock, personal injury, or death, disconnect electrical power source to unit, unless test
procedures require power to be connected. Discharge capacitor through a resistor before attempting to service.
Ensure all ground wires are connected before certifying unit as repaired and/or operational.

Defrost Heater

The unit uses a heater to help remove ice
build- up during the defrost cycle. When the
defrost terminator closes, voltage is supplied
to the heater via the control board.
1. To access the defrost heater, (see freezer
fan access section). With back cover
removed, the defrost heater is clipped to
the bottom of the evaporator. Remove the
clips, remove the heater, disconnect the
wiring, and replace/repair as needed.
2. With the main power switch OFF, the
defrost Heater can be tested by removing
the orange wire off of terminal E6 on the
HV board. Using an ohm meter, check the
brown wire and Neutral and you should
read approximately 30 Ω. During the
defrost cycle line voltage passes through
the Defrost Terminator the into terminal
E5 (orange wire). With the defrost heater
relay activated, the voltage exits the HV
board from Terminal E6 (orange) to the
heating element. If voltage is present at
E5 but not at E6, then the Defrost relay is
open. If there are 0 volts at E5, then the
terminator is open.
©2012 Viking Preferred Service
! WARNING

Defrost Terminator

The defrost terminator is a bimetal switch
that is normally open. Below 20+/-8.5 ˚F,
the terminator is closed. In order to test, first
switch the main power switch to "OFF", then
locate the brown wire on E5 of the HV board.
Unplug the wire and check for continuity
between the brown wire and the black wire
at E10. In the defrost cycle, this circuit will
supply line voltage to the defrost relay.
1. To access the defrost terminator (see
freezer fan access section). With rear
cover off, defrost thermostat is located
on the left side of the evaporator. Un-clip
the terminator, disconnect wiring, repair/
replace terminator.
Disassembly
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