So my stepdad and I decided to fix my non functional rear defroster by going to the wiring underneath the right footboard, and doing a direct connection through a burnt out wire for the defroster, but a couple of days later my battery immediately died, and I had to get a new one. Now whenever I unlock the car i hear a clicking noise that comes from behind the dash. After a minute or so it goes away. What could be causing it?

 

Most likely it is a failed actuator for the HVAC controls. These cars have a few of them to help control temperature and air flow. I believe on the 06+ Montes and Impalas it's a more common failure than the earlier years.

 

The clicking is the actuators as Maniac say's there are a total of 3. If I remember 1 on the drivers side 2 on passenger side. I had to change mine years ago. Lots of patients because they are in an impossible place, you will work partly by feel. They are cheap plastic. I think they cost about $20. each.