Anyone ever have issues getting the rear defrost to come on? If I push the button it will either do nothing, blink one once and shut off, or I keep pushing it and it stays on. It is the rear slider and I have the heated tow mirrors that come on at the same time. Anyone else have this happen?

 

I had this problem and finally figured it out what the it was. Although the rear power slider appeared to be fully closed, it wasn't. I opened it all the way and then held the close button until it seated fully shut. Hit the rear defrost and the light came on and stayed on with the defroster operating on both the rear window and the mirrors. Try this and see if it works for you....

 

Mine is at the dealer now with the rear window out of it.
They couldn't get the defroster working completely right and are now replacing it.
I never wanted the sliding rear window, it just came with the truck. I don't think I will be opening it at all anymore.

As Coaster said, the defrost is tied into the rear window being closed all the way. If open, it will not turn on.

 

I had this problem earlier this year. I went to use the mirror heat and nothing happened. They found that the rear defrost was bad and changed out the rear window, and it has been working great ever since.