Hi and welcome to FixYa, I am Kelly,
This particular unit was made in both a top mount and a side by side:
Which one is yours?
It is difficult for me to post a proper solution without knowing which unit you have. Having said that..there are many things to check.
1. Feel the cabinet where the door gasket mates to the chassis. It should be warm to the touch but not quite warm or HOT. If you notice that it is quite warm to hot.. open the back of the unit by removing the fiberboard cover behind the compressor. Check the condenser coils for blockage and the condenser fan for proper operation. Clean off the coils and fan with the unit unplugged. Also clean out the drip pan and ensure that the END of the compartment drain tube is free of obstructions. The unit must remain off for at least 15 minutes anytime it is unplugged so that the compressor will restart properly.
2. Inspect both doors to make sure they are properly mating with the chassis and that none of the gasket material is torn. Any air gaps can cause the symptom you describe.
3. The 253.64802 was ice maker capable. If you have an ice maker reach back behind the ice maker and check the rubber water fill tube for ice blockage. If it is blocked with ice most likely the ice maker inlet water valve is bypassing water when it supposed to be off. This makes sheets of ice on the bottom of the freezer compartment and in the ice bin. The only remedy is to replace the water valve as they are not repairable.
4. If the back wall is all frosted up or there is ice protruding through the access panel vents you will have to do a manual defrost. The is done by unplugging the unit.. removing the freezer contents and directing an external fan into the freezer compartment for just over 2 hours. (Water mess)
After the 2 hours clean up all the residual water and return the unit to normal service.
Should you have an automatic defrosting circuit problem the frosting routine on the back wall will repeat in 2 - 5 days depending upon how many times the freezer is opened. Automatic defrost problems are most often caused a failure of one of the following components:
a. Defrost control
b. Defrost heater
c. Defrost temp sensor / thermostat (depending upon model)
If any one of the above fails the automatic defrosting process will stop working. However if the temp sensor / thermostat fails it usually results in the compressor not starting at all so the problem will most likely be a. or b. above.
5. The evaporator fan motor in the freezer compartment may have failed or is not running at full speed. Make sure the fan is running. If you do not hear the fan running.. make sure you check it again after doing the manual defrosting procedure listed above. Ice build up will lock an evaporator fan blade in the ice and you may be tricked into believing the fan is bad when it was just frozen in place.
The steps above will most likely help you identify the problem.
I really need to know which one of the units you have the 253.64802 or the 106.64802.
You can find parts for your unit by going to http://www.searspartsdirect.com
and doing a Model search near the top of the page. The model number is entered just as it appears above.
Thanks for choosing FixYa,