2013 Toyota Tundra Double Cab Owners Manual - Page 466

3 -8 . Ot he r int e rior fe a t ure s Se at he at e rs a nd ve nt ilat ors ∗ Blows air from the seats The indicator comes on. The higher the number, the stronger the airflow becomes. Heats the seats The indicator comes on. The higher the number, the warmer the seats become.