My 6 Yr old Frigidaire Upright freezer gets down to the 50\'s and will not go any lower. I think I have a freon leak. What do you think?The compressor is running. (I put in a new run capacitor to make sure.)I installed a new defrost timer. (The old one tested good but I installed a new one anyways.)The temperature control thermostat tested good at 70 F, (Continuity) I tested it at 13 F and it had continuity also. I believe the temperature control thermostat should be open circuit so may its bad again. I replace it two years ago.There is no ice buildup on th coils. In fact there is only frost on the first coil at the reduction tube. Thus I think I am low on freon. I gave it a shot of freon and the coils got frost for one day and then the frost dissipates. The coil fan inside of the freezer runs constantly.Either I have a freon leak or another bad temperature control thermostat.What do you think?Any help is appreciated.