Diagnostic help needed. Fridge was warm. Freezer had ice blocking vent. Replaced defrost heating element and defrost thermostat. All worked well for 6 weeks, then it happened again Tuesday. Unplugged and defrosted for two days. Plugged it back in yesterday and all seems well. Fridge is cold and ice maker is making ice. Old fridge. Don't want to pay $$$ for repair or sink too much $$$ in troubleshoot guessing. Any idea as to what this could be? Way to troubleshoot? Since the heating element and thermostat are new, it seems like it's not being "told" to turn the defrost cycle on and off correctly.