Unplug the unit from the wall.
Remove the mounting screws from the air baffle cover toward the side of the freezer. Pull the cover off.
Release the air baffle retaining clips from the top of the freezer. Push the baffle into the hole.
Pull the wiring out from the baffle.
Set a multi-tester to the X1 setting. Turn the baffle to the highest setting. Touch the probes of the multi-tester to the terminals. The multi-tester should read infinity. Change the baffle to the coolest setting. The tester should read zero. Replace the unit if you receive a different reading.