I have a stainless Frigidaire side by side model number: LFUS2613LF1 fridge the my grandfather gave to me because he was having trouble with it. I cleaned it up (under side coils as well), and plugged in to see what it was doing. It worked well for about 3 days (temps -3 freezer & 33 fridge).....then temps on both dropped. I saw that the freezer back wall was freezing up, so did some reading & decided to trouble shoot.1) tested continuity in the defrost heater....& tested ok.2) tested the defrost thermostat (multimeter for continuity while putting it in a upright freezer....& tested ok.3) replaced the defrost control board ( part # 242053503) with a new one. This made the fridge freezer ok for a few days....then back to a beeping on day 3 due to temps same as before freezer 10+ freezer & 50+ fridge.I have tried resetting by killing power...defrosting quite a few times....I AM AT A LOSS!P.S. I have photos of all but can not figure out how to attach them here. They are 6-8 mb, Too big?Any help is how to troubleshoot from here would be greatly appreciated.