The illumination of my dashboard (the tach, speedometer, etc) is always on. I wish to have it off unless my headlights are on.

Not having the ability to leave my headlight switch on all the time, I have been delayed in turning my headlights on around dusk.

 

On my 2015 tC, there is a way to leave the headlights on all the time. I leave my switch on constantly, and when I arm my car's security, I hit the lock button twice when I get out of the car. It automatically switches my headlights ans fogs off on the second push. But if you want to turn the dashlights off, you should be able to turn the dimmer all the way down, mine goes all the way down to fully off.