If one headlight is not functioning, where should the initial check begin?

The initial check for a non-functioning headlight should begin on the headlight side of the circuit, as this area is where the specific issue with that headlight is most likely to be found. By focusing on the headlight side, the technician can assess the wiring, connections, and the headlight bulb itself. It's feasible that a burnt-out bulb or a poor connection could be the root cause of the failure, and checking here first allows for a straightforward inspection of the most common issues.

Examining the headlight switch or the battery as starting points is valid in other circumstances, but they would typically be addressed after confirming that the headlight itself or its immediate circuit is functional. Checking the fuse box can also be a later step if there are signs of an electrical issue or if more than one headlight is not functioning. Prioritizing the headlight side of the circuit streamlines the diagnostic process by tackling the most likely source of the problem first.