Self defrosting deep freeze not defrosting

It sounds like you might be dealing with a defrost drain issue or a problem with the freezer's door seal. Try defrosting the freezer and clearing any ice buildup, then check the door seal for any gaps or damage. If the problem persists, you may need to consult the user manual or contact a professional appliance repair service for assistance.

I've just had a similar problem. I fixed it by removing the large panel on the back of the inside of the freezer. I found a large build up of ice at the bottom of the freezer which seems to have developed because the drain hole at the bottom of the freezer was blocked. I defrosted the ice, cleared the drain and now the freezer is working fine.

evaporator coils is probably frosted from condinsation.shut door set at normal setting and give some time.

That is normal. The refrigerant runs through those shelves. They are the evaporator side of the unit.That is where the freezing effect comes from.
Check door seals for leaking air.
Keep door openings to a minimum.
Get in there and get out.
Those things will help prolong frost/ice buildup.

Check condenser fan to see if it's working. It's the fan next to compressor

Sounds like a blocked defrost drain. By "American" I presume you mean side-by-side.
I had a similar problem with a freezer-on-top style Samsung. The solution to that was to defrost the freezer, remove the false backing plate in the freezer (required removal of the ice cube tray. the panel just pops out with a bit of pulling). The drain hole beneath the freezer coils was blocked with ice. This drain passes down into the fridge and then out the back of the fridge into the evaporation pan next to the motor. There is a collector pan under the freezer coils, this and the drain hole were filled with ice. When the freezer goes into its self-defrost cycle the water collects here and then overflows into the fridge.
I removed the ice with hot water/vinegar mixture (so it doesn't re-freeze immediately) and simultaneosuly used a bit of chiselling with a screwdriver to clear the drain plug. I did this from inside the fridge working up the drain hole into the freezer. The whole job took about an hour.

Was the door left open for a long period of time.? Sometimes this causes so much ice that it re freezes and can't clear the drain. The only solution is to unplug and let sit with doors open for at least 24 hours. to get all the ice off the coils. Then use a pipe cleaner on the drain then use a turkey baster to force water through. then a mild bleach solution. Check the door gaskets if they are ripped or loose or the door warped and not sealing tight this will also cause this problem. If this still doesn' t solve the problem it is probably a defrost problem Usually the timer or defrost thermostat.

The reason for ice buildup is an air leak. Recheck all around the gasket by taking a dollar bill and closing the door on it and pulling it out. If you don't have resistance, you found your leak. Heat that area with a blow dryer to relax the gasket and close the door to let the magnet and seal set. Also, rub some vasoline on the hinge side gasket to keep it from dragging.

I would check that the door gasket makes good contact with the cabinet. If it does then I would check the temp inside the cabinet. If you have large buildups of ice on the evaporator coils then I would suggest defrosting the freezer and see if that makes a difference. Hope this helps.

I looked at the BACK at the bottom underneath of my Sears Kenmore frost free upright freezer and what was causing the ice buildup was very simple. At the factory, the assembler looped the little hose too high and when the water went into the hose it could not get out due to being too high in one spot! An ice dam will form, blocking ALL water coming through
and freezing up any more water coming down giving you a HUGE wad of ice that is scary!!! I just removed the screw holding the loop that holds the hose and put a bit of warm water down the little hole on the INSIDE (Behind the grate) to melt the remaining ice in the tube.You need to take out 4 screws and remove the grate to see this. I could not believe that this was the problem! I haven't had any ice build up since.Now don't tear your freezer apart before you try this trying to fix the compressor, thermostat etc. It may be the only thing wrong with it!