If your vehicle is showing instrument cluster backlighting is completely dark, here are the most likely causes and the parts you'll need to fix each one.
A blown fuse is the most common reason for the cluster lights to suddenly go dark. This is frequently caused by a short circuit, especially if an aftermarket stereo was recently installed and the illumination wire was grounded.
The interior dimmer switch may have been accidentally bumped to the lowest setting, or the switch's internal contacts have worn out and failed to send power to the cluster.
The headlamp switch routes power to the interior illumination circuit. If it fails internally, the cluster lights won't turn on even if the exterior headlights do.
In older vehicles with incandescent bulbs, it's possible for all the bulbs to eventually burn out. Often, owners don't notice the gradual dimming until the final working bulb fails.
The instrument cluster itself may have a failed internal power supply, broken solder joints, or a dead LED driver, requiring repair or replacement of the entire unit.
In modern vehicles, the BCM controls interior lighting. A fault, internal short, or software glitch in this module can prevent the cluster backlighting from activating.