Arrived at location 7/12/22 - Arrived and found ice all over the floor and ice build up around the drain pan. I turned the unit into defrost and made sure defrost works. I then removed the food racks from freezer as I could not work on the unit. I then dropped the drain pan and seen that it was completely frozen solid. I tested the drain line heater and have proper voltage but the heater was not working. I shut the unit down and removed the old insulation and drain line heater. I then melted the drain pan and melted the drain line until I could see water draining out of unit. I then installed new drain line heater and insulation and turned the unit back on. The drain line heater is now working