why does my heater only work in certain positions?

What is your question?

so i my ac works fin and the heat will only work sometimes and only in certain positions. like, if i turn my heater all the way up on the right it blows out cold air, but if i turn my heater somewhere in the middle of the hot air it'll blow out heat. a/c button is off and temp gauge gets to a normal operating temperature

What makes this problem better or worse?

nothing that I've noticed

How long has your 2006 Toyota Highlander had this problem?

couple weeks or so