What does the main relay do and how do you know when it needs replaced?

The main relay in a vehicle controls the power distribution to various electrical components, including the fuel pump and ignition system. It typically operates when the ignition key is turned on, allowing current to flow to these systems. Signs that the main relay may need replacement include intermittent starting issues, the engine not starting at all, or the fuel pump not activating. Additionally, a clicking sound from the relay or visible damage can indicate it has failed.