When there is a headlight fault, what is checked first?

When addressing a headlight fault, the first step is to check the external light controls MCB (Miniature Circuit Breaker) in the local driving cab. This is because the MCB serves as an essential safeguard in the electrical system of the vehicle. It is responsible for protecting the circuit from overloads and short circuits, and can often be the source of a failure if it has tripped. By inspecting the MCB first, one can quickly determine if the issue is electrical and requires resetting or replacing the breaker.

In contrast, although examining the headlight bulb, battery voltage, and circuit wiring are also important steps in fault diagnosis, they are typically secondary checks. If the MCB is in proper working order and has not tripped, then further tests can proceed to assess the bulb itself, the battery's voltage, or any potential wiring issues. This systematic approach allows for efficient troubleshooting without overlooking critical components in the circuit pathway.