Good afternoon i have a ge upright freezer it is not an auto defrost model was getting severe frost buildup in unit thought it was the seal as had gaps and cracks in seal replaced seal zero gaps magnet seals all the way around perfect.Cleaned freezer let run empty for 36 hours getting frost un upper coils already compressor is running only gets to 20 degrees
Here are your parts
Parts for GE FUM21DMDRWH Freezer - AppliancePartsPros.com
Check to make sure that the interior light shuts off when the door is closed.
I am assuming that the compressor is running all the time.
If it is cycling then you may have a control thermostat problem.
Frost on the coils is normal. Any humidity in the air will condense and freeze onto the coils. I am not sure how long it takes for this unit to get down to normal temperatures when it is empty. I would give it some more time.
Now for what could be bad news. When frost develops only on coils that that are the closest to where the freon enters the evaporator it is an indication of a sealed system problem (often low freon).
If this is the case it will be an expensive repair as you need a pro.
Often it makes more sense to put the dollars towards a new unit.