My bottom freezer defrosted overnight. What number should it be set at for optimum performance. I have a kenmore 67942 about 10years old.

SOURCE: Kenmore Elite Bottom Freezer Mod. #795 75544401

While the freezer is cold, cut out defrost thermostat and measure resistance, if open, replace, if it's ok check defrost heater.
Temporarily short the wires that went to the defrost thermostat and now force defrost.
If no defrost, you have a bad adaptive defrost board.

SOURCE: Freezer not defrosting

Hello pumpguy2
Welcome

You said, you have a Kenmore bottom Freezer Model 596.73503201. It works fine but the freezer has stopped defrosting. Any suggestions?

It is supposed to be auto or self defrosting.
What do you mean you are getting ice forming in the freezer?
Waiting for your response and more detailed explanation.
Huuum

SOURCE: Kenmore Bottom Freezer Refrigerator

hi In some cases, a faulty thermostat may not be the cause of a warm refrigerator or freezer. A warm box may also be caused by a defective fan, a blocked fan, or broken or bent fan blades. If the blades are jammed, try to free them. If they're bent, straighten them with pliers. If this doesn't solve the problem, call a professional service person.

On some refrigerators, the door switch operates the evaporator fan. If the fan seems to be malfunctioning, the door switch could be faulty. Test the switch as detailed in the last page, and replace it if necessary.

SOURCE: Whirlpool side by side refrigerator not defrosting.

take back panel off inside freezer. check continuity thro heater and thermal fuse in series with heater

SOURCE: kenmore elite bottom freezer icing up

if it has an ice maker fix or adjust the over flow for the ice try.