If you need a new thermostat, below is a link to the thermostat you'd need to order for your model.
CLICK HERE for thermostat
Now that being said, if the thermostat was bad, it would keep turning the refrigerator off because it thinks it's up to temperature even though it's not. On the other hand, if the refrigerator is constantly running and not getting down to temperature, then the thermostat isn't your problem.
If the fans are running but the freezer is thawing, you have an issue with your sealed system unit. In other words, it means that means that the thermostat and defrost timers are working properly which means that either you have a freon leak or the compressor is just bad since you already replaced the overload relay. Now if the compressor is humming along and running, then you may have a freon leak. If the compressor is not running or its trying to run every once in a while and cutting out, you definitely have a bad compressor since the overload relay was already replaced. Freon leak repairs are not something you can repair yourself and neither is replacing the compressor I'm afraid. To recharge a freon system it costs about $350 and to replace the compressor it's about $550 if you wanted to stick that much money into the refrigerator.
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