What would likely cause dim lighting if half of a dash is dark?

A defective dash light dimmer is a likely cause of dim lighting when half of the dash is dark because the dimmer controls the brightness of the dashboard lights. If the dimmer switch is malfunctioning, it may cause uneven brightness across the dashboard lights, leading to a scenario where only part of the dash appears dim or completely dark. This can happen if the internal components of the dimmer fail, resulting in inconsistent power delivery to the bulbs.

In contrast, while a faulty battery connection might cause electrical issues in various systems, it typically wouldn't lead to just half of the dash lighting being affected. Similarly, a blown fuse would generally cause a complete failure of all related circuits rather than a partial effect. An overload in the electrical system could cause various electrical components to malfunction, but it wouldn't specifically lead to only half of the dash lights being dim. Therefore, the malfunctioning dash light dimmer’s role in controlling light intensity makes it the most direct cause of the described problem.