When the dash lights in a car don't come on, but the headlights work, it typically indicates an electrical problem. This could mean that a fuse has blown, wiring has frayed or corroded over time, a short circuit has occurred in the system, or an automotive computer component is malfunctioning. Other potential causes include a dead battery or degraded battery connections. It is important to have any issues fixed right away, as they can cause safety hazards while driving.