2001 Chevy Venture dash lights go out

my dash lights work perfectly until the driving lights are either turned on with the switch, or when they turn on automatically, then the dash lights turn on, including the illumanation lights for the heater panel and the stereo dont work at this time. but when i turn the car off, they work again until i turn the car on and the head lights turn on again and the dash lights go out again. it does not matter, when ever the head lights or parking lights are on, the dash lights go out.