The evaporator coil behind the cover on the back
wall inside the freezer will ice up under normal conditions. Every 8 to 10
hours for around 20 minutes the defrost timer (or in most newer models the electronic
adaptive defrost control) will turn the defrost heater on to
melt the built up ice. There is a defrost thermostat which prevents the heater from
overheating the freezer by breaking the heater circuit when the temp reaches
close to 32 degrees F. The entire cooling system shuts off during the defrost
cycle and starts back when the timer advances through the cycle.
If this ice is not melted it will continue to
build up until the air can’t flow over the coil to circulate the cold air
through the freezer and into the fridge. The temperature change in the fridge
is usually noticed first followed by the freezer.
If the defrost thermostat is bad it can prevent the heater from
coming on OR it won’t turn the heater off when it gets too warm. It is clamped
to the evaporator coil at the top to sense the temp. If it appears to be
misshapen it is bad.
With an ohm meter it should show continuity when
cold and none when warm.
You can also bypass the thermostat to see if the
heater comes on then. If it does then you know the thermostat is bad and needs
replaced.
The defrost heater is
located on the evaporator. It is in a tube which is at the bottom and can also
go up the sides of the evaporator. On some types you can see a burnt spot if
it’s bad. With an ohm meter it should show continuity from end to end when
disconnected from the wiring in the freezer. You can also test the wiring for
voltage when it’s in the defrost mode.
If
you have a defrost
timer you
can test it. It can be located under the fridge behind the kick panel on the
front. Some are in the fridge with the controls at the top. You can turn the defrost timer till it clicks and everything shuts
down. The heater should now come on. If it does, replace the timer because that
means the timer is not running. If it
doesn't, check the heater and defrost thermostat. Turn the timer again till
everything starts back up to end the defrost cycle.
If you have an adaptive defrost control instead of a timer,
replace it if the heater and thermostat test good. It is located in the fridge
with the controls in some models and on the back in others.
If you need help finding your model number see
here> http://www.appliancepartspros.com/modelnumber_locator.aspx
To locate your timer, motherboard, control or adaptive
defrost control , enter your model number and search for the part or post back
on Fixya.
http://www.searspartsdirect.com/partsdirect/index.action?psid=26129238&sid=PSx20071217x00001a
This problem seems to be two sided. A refrigerator
defrost it is supposed to take the water from defrost down a pipe located
behind the freezer rear wall to a pan below the refrigerator where there is a
fan blowing warm air over the water to evaporate back into your home or
business. If that drain is blocked your refrigerator will accumulate a large
block of ice and frost behind the rear panel of freezer and temperatures will
warm considerably in fresh food compartment and freezer. Here is one site I want you to read over=> Leaking Refrigerators Just What may Be Happening and here=> Leaking Refrigerators here is a link to a service manual=> LFX25960xx Service Manual Let
me know if this service manual is close enough to your model number. At this point I am looking for air blockage behind the rear panel of freezer. If air is being blocked by ice and frost you can use a hair drier to help speed you up while melting ice. If drain is blocked use whatever you can to open the drain line mentions on the links I sent you to and let me know what is found, Thanks Sea Breeze
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