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Re: the unit begins a defrost cycle without warning
In general, a freezer will go into a defrost cycle about every 6 hours and usually from 25 to 40 minutes. After the defrost, the unit should function normal. Pull down to temp and cycle off. If the product shows signs of thawing, then I would be concerned about the box temp. Defrost may be too long or some other issue may be effecting it. Otherwise, if no signs of thawing, I wouldn't be too concerned. It's the product condition that is the concern.
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Defrost cycle usually comes on after about 7 hours. If it is happening every 30 minutes or so, the defrost timer is not working properly and your internal temperature will never have a chance to go down to zero as SOP.
When defrost cycle comes on, the compressor is automatically shut off and internal freezer temps can go up by close to 25 degrees or more. It is for this reason that commercial freezers do not have auto defrost - the latter extols a price, convenience at the price of higher average temps and less time to properly store foodstuffs in freezer.
If refrigerant charge is ok, make sure that the evaporator coil is not covered with ice. The latter serves as an insulator and will keep unit from achieving designed low temps. Remove ice by defrosting unit manually and then restarting unit. If ice continues to build up at alarming rate check for the tightness of door gaskets. If lots of moisture gets into unit, it will collect and freeze on coil. Also check to see that the defrost timer is not going on excessively. Those defrost cycles can raise internal temps by as much as 25 degrees; if the cycles come on prematurely and/or very often internal temps will be high.
If the defrost timer sticks in the defrost mode,yes. Normal defrost time is 30 minutes or less depending upon which timer is installed. If it happens again,locate the defrost timer and turn the dial manually to see if the compressor comes back on. If so,replace the timer. It is probably on the rear near the compressor. Some are under the front behind the dust guard.
DO NOT TRY TO MODIFY TIMING CYCLE.you would need to completely modify printed circuit board and inbuilt computer......some freezers cycle around 6 to 8 hours.the temperature can only be checked say every 12 hours to get an average reading
Most all commercial freezers have a fan delay/ defrost terminator. It is usually mounted on the end of the evap coil. It's purpose is to sense the temp of the coil during the defrost cycle. When it hits a preset temp., usually around 55 degrees or more (depends on Mfg.) It terminates the defrost cycle. It also doubles as a fan delay. It allows the evap coil to cool off from the defrost cycle before allowing the fan to come on. Usually, the coil has to get around 20 degrees before fan will energize. I would look for this as a possible problem. It could be one device with 3 wires or 2 separate devices with 2 wires each. I've seen it both ways.
Hope this helps.
Check to see if the
condenser fan at the back underneath near the compressor is running. If no
How to check stuff> http://www.acmehowto.com/howto/appliance/refrigerator/refrigerator.php
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 heateris
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
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
It is probably the control board and since it's new it's still under warranty so a certified Frigidaire repair man will fix it without charge. There should be a telephone number with the paperwork you received when you bought it.
In most cases, an evap that freezes up is either an air flow problem or no defrost cycle. Older Hobarts have mechanical defrost time clocks. It could be locked up i.e., not running so no defrost cycle.
It could be coming out of defrost too early because the sensor that monitors the evap temp is not working properly.
The door could not be closing. If left cracked open, it will freeze up every time as unit never hits temp., keeps unit running. Warm air is seeping in and the moisture freezes on evap.
Lastly, the defrost heater(s) may not be working. Burned out, shorted, broken wire, etc.
The freezer should stay within 5 degrees of 0 while in operation. While in defrost the freezer may reach as high as 20 to 25 degrees. If any higher temperatures are reached your food will spoil as they are defrosted and refroze everyday. If you find that the temperature is allowing your food to defrost you may want to replace your defrost thermostat. This device is located on top of the evaperator coil inside the back of the freezer. It is made to turn the heater off when a temperature of 55 degrees is reached. One other possible problem could be your defrost timer is taking to long to restart the cooling cycle after defrosting. I hope this will help you and please send any other questions you may have, I am happy to help. and dont forget to rate me.