To find it, you'll likely need to:
* Consult your vehicle's repair manual: This is the most reliable source. The manual will have diagrams showing the location of all major components.
* Search online for a repair manual specific to your year and model: Many are available online as PDFs.
* Use a visual inspection: This will require some disassembly of the dashboard, and could be quite involved. Be prepared to remove parts carefully.
Warning: Working on the dashboard and ventilation system can be complex. If you're not comfortable working on cars, it's best to take it to a mechanic. Improper disassembly can cause damage.