Bought Used about a week ago. plugged in worked fine. For some reason the previous owner was using an external water filter instead on the internal one. Put on a new supply line without filter. the internal filter bypass plug installed. the internal water dispenser didn't work nor did the ice maker. two days ago, food in the freezer started defrosting but fridge section still seemed cold. Yesterday installed an internal filter and the water dispenser did work. the fridge now has gotten warm as well. removed back panel, the compressor seems to be running and was hot to the touch the fan is running as well. Opened up the freezer panel Fan also running there. there was frost and ice on the copper tubing leading to the coils. did a force defrost and heating element didn't get hot. tried twice still nothing. Assumed it was defrost thermostat, ordered one. put all back together. since ice and frost melted I assumed it start cooling again. and was hoping it would stay cool until the defrost thermostat arrived. that wasn't the case it hasn't cooled at all. any suggestions on things to check and how to test them would be greatly appreciated.