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Goes into defrost, but takes too long to kick back on. The ice cubes will melt. This is happening sporadically. There are no clicking noises, but the refrigerator does run longer. Called a repair man, but could not find a problem. Was working perfect for him when he had it at his shop for 2 days. Could this be the mother board?
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Rank: Advanced Member
Groups: Senior Expert
Joined: 3/10/2009(UTC)
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Your defrost thermostat is supposed to turn the defrost heater off before it can start melting everything. Without a working thermostat the heater will stay on for the entire defrost cycle, normally around 20 minutes.
How long is yours staying in defrost? Part 620 on diagram 4 is your defrost thermostat.
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Rank: Member
Groups: Registered
Joined: 6/11/2009(UTC)
Posts: 2
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Originally Posted by: woodchuckie  Your defrost thermostat is supposed to turn the defrost heater off before it can start melting everything. Without a working thermostat the heater will stay on for the entire defrost cycle, normally around 20 minutes.
How long is yours staying in defrost? Part 620 on diagram 4 is your defrost thermostat. I thought the defrost thermostat was a safety to turn the heating element off if the defrost timer or adaptive defrost control board failed. I am going to guess it's the defrost timer, or adaptive defrost control board that's bad. depends on the frig you have. They are not turning the heater off in time so the thermostat kicks in as a final precaution before the freezer gets too hot/warm.(maybe preventing a fire) By time the thermostat kicks in the melting/thawing of the food has started. After a bit the timer stops powering the heater and tells the compressor to start and the freezer cools down again. Then repeats. I could be wrong I just started to look into this myself. I noticed my sealed foods started to grow more ice crystals. This had me thinking, then last night I found liquid water in some sealed containers. At that point I opened the back of the freezer and disconnected the heater. this was a temp fix until I could read up on the problem.
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Rank: Advanced Member
Groups: Senior Expert
Joined: 3/10/2009(UTC)
Posts: 1,363
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The defrost thermostat opens(cuts heater off) at around 32 degrees before anything in the freezer can thaw. That is the temp about 1 foot above the heater. The difference in the temp of the frozen food would not be noticeable.
If the defrost timer quit running during the defrost cycle, the heater would come back on if the defrost thermostat temp got below freezing again. Otherwise the contents would gradually thaw but not refreeze because the timer also cuts the compressor and fans off and would not turn it back on because it's not working.
I hope this helps with your problem too.
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Rank: Member
Groups: Registered
Joined: 6/11/2009(UTC)
Posts: 2
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Originally Posted by: woodchuckie Your defrost thermostat is supposed to turn the defrost heater off before it can start melting everything. Without a working thermostat the heater will stay on for the entire defrost cycle, normally around 20 minutes.
How long is yours staying in defrost? Part 620 on diagram 4 is your defrost thermostat. It has defrosted for hours in the past, but more recently in the last two weeks it has stayed on long enough to melt the ice cubes half way before it cooled off again. I will try replacing the defrost theromostat. Thank You.
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Rank: Member
Groups: Registered
Joined: 6/11/2009(UTC)
Posts: 2
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Is it posible the defrost timer is running too slow? That would cause a long defrost period. I guess the only thing i can do is take a multi meter to the defrost thermostat and see what temp the circuit is open and closed. if it stays closed at too high of a temp it would need to be replaced. If its border line and a little high, Maybe i can move it closer to the heating element. That should cause it to open up faster and prevent it from heat up the freezer too much. heres a nice site i found showing how the parts work. http://www.appliance411.com/faq/howdefrostworks.shtml
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