doubts

They know to explain my Cupra 2 makes a strange racket, when it puts the Ac in auto! I no find natural! Thanks

Hi, I've just read about venting and I'll give it a try. However I have a doubt. Without venting when I fill it up the pointer always points to full tank. If what people say it's true (about not really getting the tank completely full) than shouldn't the pointer stop a bit before full tank...