Kenmore Upright Freezer

I have a Kenmore upright freezer. It is between 2-3 years old. The top is not cold at all, but the very bottom will still stay frozen. Now it is beeping shoing high temp. Is there anything that is a regular problem on these or should the freezer be replaced?

If it's the kind where the shelves are the evaporator coils(that's where the frost forms) and only the bottom gets any frost then it's low on freon. It's leaking somewhere.

If the evaporator is behind the rear wall inside the freezer then the evaporator fan may not be working.

There has never been any frost on the shelves. It has frost right now on the back wall at the very bottom where the cover panel is.

Yours is an auto defrosting unit and it sounds like a defrost system failure. It could still be a freon issue. Remove the cover on the rear wall inside the freezer and see if the frost is on all the coils or just part of it. With low freon just part will have frost on it.

Here is a description of the defrost system for a fridge which is the same for a freezer.
DEFROST PROBLEM
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(disconnect the two wires plugged into it and twist them together) 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 heater is 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 timer you 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.

I removed the back panel and the entire coil is iced up. I unplugged the freezer to allow it to thaw. The fan above the coil is running. Do you think it is the heater or the defrost timer?

It could be any of the three components. The heater is what I would check first since you have already accessed it. Unplug it and check if for continuity.