why dimple in middle of hot/cold knob

[punch]

Originally Posted by fearturtle44

You don't need the dimple because you have the blue and red markings. But if the dimple is so important, then how do you know "if the heat is on full" at NIGHT as the dimple does not light up??? I would agree if the markings weren't on the dial.

Just an update I am wrong, i looked at my dial and yep the "needle" lights up and the outside ring turns not the whole knob, i wonder if those euro.. cars have a different knob and they need the dimple??