no panel lights when you turn on headlights on 1994 Chevrolet Suburban 1500

when i turn on the headlights the instrutment panel lights and the heater light goes out all the guages and signal,high beam check engine and brake indicators still work i have headlights and the park lights still work.. i have checked all the fuses and bulbs and replaced the headlight switch

Asked by for the 1994 Chevrolet Suburban 1500