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Defrost Heater
The defrost heater is a single-tube, glass-enclosed
radiant heater. It is held in place by 2 tabs on the
evaporator (1 on each side) and by a ceramic and
wire support.
The defrost heater has an approximate resistance
value of 31 Ω.
If an open defrost heater is suspected, perform step
#1 of the return duct heaters test. (See Return Duct
Heaters.)
For a resistance reading other than approximately
27 Ω, remove the evaporator cover. (See Evaporator.)
Disconnect both leads from the defrost heater.
Connect a volt ohm meter to the heater terminals
and check for the resistance value of approximately
31 Ω.
To remove the defrost heater:
Access the freezer evaporator. (See 1. Evaporator.)
Note
During defrost, the drain probe assists in •
preventing the drain from icing closed. During
assembly, the probe must be installed on the
evaporator and inserted in the drain to prevent
drain freeze-up.
A ceramic and wire support prevents the heater •
from sagging and touching the metal drain
trough if the glass is broken.
2. Remove the ceramic and wire support, and the
drain probe from the evaporator.
Bend the aluminum tabs back (located at each 3.
end of the defrost heater) and lower the heater
out of the evaporator.
Disconnect 2 lead wires and remove the heater.4.
Drain Probe
Ceramic and Wire Support
Return Duct Heaters
A return duct heater has been added to each of
the 2 fresh food compartment return air ducts. The
heaters prevent water from freezing and blocking
the airfl ow in the ducts. Restricted ducts can cause
warm fresh food temperatures. (See Airfl ow.)
Return Duct Outlets
The heaters operate with 120 VAC and each heater
has an approximate resistance value of 440 Ω. The
heaters are in a parallel circuit consisting of 2 duct
heaters and the defrost heater. The line voltage
wires of the duct heaters are connected to the blue
wire of the defrost heater. The neutral wires of the
heaters go through the overtemperature thermostat
(model PFSF2), or the defrost thermostat (model
GBSC0). The 2 duct heaters are energized (along
with the defrost heater), during the defrost cycle
when the overtemperature thermostat (model
PFSF2), or the defrost thermostat (model GBSC0) is
closed.
Return Duct Heaters Test
If open duct heaters are suspected, perform the
following:
With the overtemperature thermostat 1. (model
PFSF2),
or the defrost thermostat (model GBSC0)
closed, on the main control board, test for
approximately 27 Ω (the equivalent resistance
of this parallel circuit) between J9 and J7-9
(model PFSF2), or CON3-1 to CON3-4 (model
GBSC0)
.
For a resistance reading other than 2.
approximately 27 Ω, remove the evaporator
cover. (See
Evaporator.) Disconnect both leads
from the defrost heater. Insert a volt ohm
meter into the disconnected leads. A reading of
approximately 220 ohms at 70°F indicates both
heaters are good.
Note: The return duct heaters are integral to the
foamed in place internal ductwork of the refrigerator
and are not replaceable.
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