1) Vacuum the coils under the front. No good: freezer still 15 degrees. More drastic measures required. 2) Pull it out and clean dust from fan exit grill (which is spinning nicely), and do my best with a brush on a springy wire to clean dust off of the nearly impossible to reach coils under the unit, still no improvement. Hmm. Begin diagnostic phase.
3) Check fan inside the freezer is running (ok) and evaporator coils (by the time I pulled the sheet metal) had no frost build-up (ok). Running out of ideas.
4) Run defrost cycle by opening/closing the door 4 times within 8 seconds, verify heater comes on (ok). Unplug to stop the defrost cycle (no frost to thaw).
5) Set the thermostat to max cool. Let it run an hour (it stays running the whole time) and check temperature of evaporator coils with non-contact instant IR thermometer. Inlet tube in the zero degree range, outlet tube in the 25 degree range, but inlet and outlet are both on the top. On the bottom (half-way through the path), the temperature was 45 degrees! Temperature of coils under the toe kick are 77 degrees, the room is 70 degrees.
So, I think I know the answer: new fridge, right? I know that replacing a compressor is not a good idea, if that's the problem, but any hope at all in adding refrigerant?
--Dale--