I have an 11 year old GE side by side (TFT20SABKWW). I know that the defrost heater was not working (frost build up on evaporative coils) and have ordered a new heater, thermistor and defrost timer. Right now, I am still running refrig/freezer, but can not get FF side down to 40 degrees. I have slide bar setting on #9 and FF temperature is steady at 50 degrees. Could this be a problem with the FF thermostat (is there one)? Or, because I don't have the heater installed and the back freezer (interior) cover off? Thank you. Debbie

If you have a cover off you will not get airflow into the refrigerator section. All covers must be installed for it to work. Check the condenser coils, too. If it's dirty and blocked by dirt the compressor will overheat and fail, plus it will not be able to cool. Iced over freezer coils will also keep it from cooling since air goes from there into the refrigerator section. DrTom4444

Thanks for your answer. I really appreciate it. I do try to keep the condenser coils clean as I have several dogs that shed. I left off the freezer back cover to keep an eye on my evaporative coils. They have frosted up some (there is no defrost heater installed at this time), and I hope to get my new parts by Friday. Again, thanks for your help. Debbie