One week ago I noticed that the freezer (on top) seemed rather warm. I checked the temp and it was 12 degrees F. I have checked the temp from time to time in the past and it was always 0 degrees F or close to it.
The fridge temp is OK - around 37 degrees F.
The repair man came over and told me the coolant was 20% low so he topped it up.
Made some difference. Now the freezer is anywhere from 6 to 12 degrees F during the day.
He said that the coils should completely frost over within 30 minutes. It took 2 hours and only half of the coils were frosted over.
I'm not comfortable with these temps. Could it be the Adaptive Defrost Control Board?
Also, does the freezer get warmer during a defrost cycle? How much warmer?
Thanks.

It's a few days later and the temperature of the freezer continues to rise slowly each day.
I just checked the evaporator coils at the back of the freezer and only one row of 4 has frost/ice on it...the rest are frost free. Is it possible that the lines have become contaminated and the drier/filter has become blocked or could I be looking at a thermostat problem? The temperature of the fridge is still OK.