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Replacement parts for FRIGIDAIRE FFU20F9GW2 Frg(v2) / Freezer | AppliancePartsPros.com

Here is the wiring diagram.
http://manuals.frigidaire.com/p...df/StCloud/216569300.pdf

Is the compressor cycling normally or does it run continuously except when in a defrost cycle?

Was the unit at room temperature before turned on an allowed to run? If yes it may take longer than just overnight to get down to set temperature.

Was the unit moved just before this problem occurred and if yes was it tilted on it's side? If yes unplug it and let it sit for 24 hours before plugging it back in.

If the compressor is cycling then it could be a thermostat problem.

If the compressor is running all the time and it does not get down to set temperature in a couple days then it could be a sealed system problem.
Remove the cover so you can inspect the evaporator coils. If there is just frost in one area (usually where the freon enters the coils) then you have a sealed ysytem problem and it will be an expensive repair. Often it makes more seense to put the dollars towards a new unit.

Note: Be sure that you do the above check after the compressor has run for a couple hours since if you check it shortly after a defrost cycle it will have little if any frost on it.

One other possibility would be a bad door seal letting warm air into the unit.