I have a 2005 Screw XLT . It is equiped with a defrost button that lights up amber L.E.D when depressed . I really dont understand what it is defrosting ? My rear window does not have the lines in it ,commonly found for rear defrost system . I cant imagine its for the front I dont see any lines there either . The owners manual is not very specific . Please Help.

 

If the defrost button is on the top right section by the ***** then its the defrost for the windshield and side windows. You do not have lines in the front window.

 

It is for the front, the windshield does not need lines since it will use the air for the heater.... My truck has 2 defrost buttons one for the window and one for the mirrors

 

As said above it's for the windshield. That's where the vents on top of the dash are there for. And on the far sides for the side windows.

 

yep, 2 buttons are used for defrost.

1 is for the windshield and door windows
the other is for the mirrors and rear window (if installed)

 

If you are talking about the one on the end of the row with the A/C button and the fresh air/cabin air button, then it is for the mirrors! I have the same thing, and it is for the mirrors, and does a great job! If you look at the diagram on the button, it kinda looks like a mirror!