Open and close degrees on a silver king SKF72D part #33338 defrost thermostat

SOURCE: have kenmore 253.54622402 side by side--from the

" waited 1 hour freezer 20 degrees // cold food side 45 degrees and no air flowing from damper " As per this it indicates that the ventilations are getting blocked after few hours.First the air was flowing from damper but after one hour it stopped flowing air from damper.Check the damper if there is too much water collected in the damper then press the damper and remove the water collected in it.------------ The working procedure of this Kenmore side by side refrigerator is as follows: --- The compressor starts then it cools the freezer section. When the freezer reaches its cooling level the defrost cycle starts functioning. In this cycle the fan in the freezer section starts running and the cool air in the freezer section is passed to the fridge section and the fresh food section gets cold. The air from freezer to fridge passes from the section, in that section the damper is located. Now this problem which you mentioned. In this problem the freezer thaws, this happens if the thermostat is not functioning or the heater is not heating. Then the ice starts getting collected on the evaporator coil. The evaporator coil is at the internal section of freezer. If too much ice gets collected then this ice blocks the fan in the freezer section from functioning and this blocks the damper section with ice getting collected there. This all procedure is controlled by the main defrost board of the unit. Now if the damper is not got blocked with too much water or if the ice is not got collected on the damper area then check the evaporator coils. If there is too much ice got collected on the coils, then takes a hair dryer and melt the collected ice. Then see if the problem returns again. But if there is little bit ice collected on the coils and fan is running properly then it's not a problem. In that case main board is faulty and it has to be replaced. The main defrost board is working but its not controlling the functions as required so the freezer thaws after few hours.

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You can get required parts from sears part direct online site or from repairclinic.com site.

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To test defrost thermostat you can test this way:---

The defrost thermostat is difficult to test since many refrigerators use different fixed temperature settings and unless you have a very accurate temperature test device the test will not provide proper results. Now you can take the defrost thermostat out of the unit and place the element only in a glass of ice water. When the element is cold it should have continunity between the two wires.------ The meter should not show a reading if the thermostat is turned off. If a reading appears, replace the thermostat.

When the thermostat is turned on, the meter should indicate "0" ohm or .3 or .2 on a digital readout. If it does not appear as "0" ohm or .3 or .2, replace thermostat.Turn the thermostat on and place each probe on either side of the thermostat so meter reads "0" ohm or .2 ohm digital. Put water and some ice in the cup. Temperature should be 32 degrees. If, after four minutes, the meter does not reflect infinite or .0000 on the digital meter open circuit, replace the thermostat.----If thermostat checked out ok then check defrost heater connection.The defrost heater is connected to the side of evaporator coil in the freezer section.If this defrost heater is faulty then it will not melt the ice getting collected on the evaporator coil and due to that defrost system will not be able to function as required.Remove the wire for one side of the heating element from the wiring and measure it for continuity, usually around 20 ohms or so.-----------

Now to see where defrost heater is located.Please click on this link below and see part number 14 on the diagram.And part number 15 is evaporator coil.And part number 21 is thermostat.

http://www.searspartsdirect.com/partsdirect/partsdirect/showSubComp.pd?imageUrl=http://c.searspartsdirect.com/lis_png/PLDM/R0405135-00006.png

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This will help. Thanks. Helpmech.

SOURCE: What is the resistance of the defrost thermostat

When the defrost thermostat is below 40 deg F, the resistance should read close to zero ohms. Above 40 deg F, it should read open. It sounds that yours is defective and replacing it should fix your defrost problem. The way it should work, is when the defrost timer shuts down the compressor and sends power to the defrost heater for about 45 minutes. The heater heats up the coil until it reaches 40 deg F, and then the thermostat opens and cuts the power to the heater so not to over heat the freezer. After the 45 minute defrost, the compressor kicks back on to resume the cooling cycle again. Hope this helps you.