No heat except at highest setting

[pt1965]

2002 yukon xl
i get cool air all the way up on the temp wheel except when i turn it past the notch at the end.
anybody know the fix for this?

 

[swathdiver]

2002 yukon xl
i get cool air all the way up on the temp wheel except when i turn it past the notch at the end.
anybody know the fix for this?

View attachment 232523

Guessing here, probably an actuator. Could be that switch but likely the former.

 

[pt1965]

a door actuator? but if its the switch,i need to replace the whole unit right?