Take away the wire from the negative end of the battery. To get to the center trim plate in newer DeVille and DTS models, take out the instrument panel. Press and keep each tab on the four corners down to unlock the A/C switch. To detach the A/C switch, loosen up the screws on models manufactured after 2006. Disconnect the A/C switch partially from its place and take off the power cords. To rephrase, setting the component back into place works exactly the same as taking it out.