You must turn off the battery's negative power connection. Take off the middle panel around the A/C Switch for drive-side Highlanders built before 2013, and for Lexus models you need to lift both floor-paneled sections covering approach to the gear panel. You'll see the mounting screws once you take off the trim; these screws are found at the bottom of the A/C Switch and audio unit on 2003 and earlier Lexus models, but four screws on 2004 and later versions. There are wire clamps that hold the assemblies together when you take off their attachments. For Highlanders, find the screws holding the A/C Switch and audio unit, take them out, pull the assembly slightly away from the car, and disconnect all wires. Unscrew the audio unit from the control panel off its brackets. In all cars made after 2004, the center trim panel now acts as a base where the A/C Switch is attached. To free the panel, pry it out from the dash with a plastic trim tool. After that, disconnect the power cables to the A/C by gently pulling the panel out. Twist off the two screws that connect the A/C Switch to the center trim panel. To take out the control panel at the back, push down with a trim tool to unlock it from where it fits in the floor console, disconnect the electrical cables, and then pull out the panel. Follow the same steps as removal to put everything back into place. Run your engine before you finish to make sure your A/C works well.