Defrost Heater; Defrost Terminator - Viking FDBB5361 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. Ensure all ground wires are connected before certifying unit as
repaired and/or operational.
The freezer section evaporator fan is a 120
VAC motor and can be tested from the High
Voltage Board (refer to High Voltage board
access).
With the main power switch OFF, remove
the yellow wire from E2 on the HV board.
Using an Ohm reading, apply one lead to the
yellow wire and the other to neutral (E9).
The resistance should be approximately
30.3 Ohms.
When the fan relay is energized, Line
voltage is sent to E2 and then to the Freezer
fan motor. If voltage is present and no fan
movement, replace fan motor.
4. Reverse procedure to reinstall.

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.
To access the defrost heater, open freezer
door and remove (see Evaporator Fan
Access section, Page 26). Remove ice
maker (see Access Ice Maker Module, Motor
and Support section, Page 23) remove
evaporator fan cover and back wall (see
Evaporator Fan Access section). The defrost
heater is now accessible.
©2012 Viking Preferred Service
! WARNING
With the main power switch OFF, the
defrost Heater can be tested by removing
the orange wire from 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 into the
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.

Defrost Terminator

The defrost terminator is a bimetal switch
that is normally open. Below 20º +/- 8.5º
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
Disassembly
Defrost Terminator
27