Running but not cooling off and frost in the back of the freezer

Unplugged the refrigerator. Removed the 4 hex head screws on the lower back panel at the back of the freezer. Used a blow dryer to defrost the pipes and area surrounding the thermostat. Unplug the connection from the back of the freezer, unplug the 2 wires, one that goes to the heater, one that comes from power. Unclip the thermostat from the pipe and note which pipe you unclipped it from. Cut the wires on the old thermostat midway between the plugs and the sensor. Using the supplied butt connectors, strip the wire ends on color matched wires (should be a dark blue or black) and crimp them together. Repeat with the other wire. Discard the white shrink wrapping. I wasn't able to get it small enough with a hair dryer or lighter. Plug the thermostat back into it's respective plugs. Clip the thermostat back onto the pipe you removed it from. Replace the back panel with the four screws. Ensure the bottom of the panel is set inside of the drip tray. Replace any shelving you removed. Plug the refrigerator back into the wall. Your done!