When my headlights turn on at night dashlights go out

Are you sure you don’t have the dash lights dimmed all the way to the off position? On the left side of the dash next to the headlight switch there should be a gray wheel you can rotate up for brighter dash lights or down to dim or turn off the dash lights. If you rotate it up until it clicks the interior dome light will come on. Try rotating that wheel at night time with your headlights on and see if they work after that. If not you have to check the dash light fuse. Reply if it does not work and I will see if I have another answer for you.