To remove the AC control unit, insert a small flat-tipped screwdriver into the left edge of the unit (the part where it meets the dashboard material) and carefully lift it out. The unit should just come out nice and easy. Once the unit is out, you can feel your way around the back of the radio or nav unit (if you haven't already removed it). You'll see the back of the ashtray compartment from there. Just route the AUX cable from the back of the radio unit down (behind the AC control unit) to the ashtray.