freezer to cold

Hi
Iwas having trouble with my freezer.No matter where I set the dial it would stay approx -10 in the freezer. The refridgerater was fine at first;then that started acting up. I replaced the t-stat; part#AP3133073. The fridge is fine but the freezer didn’t change. What should I look at next.When I ordered the t-stat I was told it controls both units.

                                    Thanx for any help:confused:

Remove the tower inside the freezer, plus the back cover. Look for an ice clog in the air returns. Turn the knob on the left side of the control panel and check the air flow round control turns freely, it might be ice clogged.