What is a ignition relay?

The relay is a device that typically uses low amperage 12 vdc electrical (control voltage) to switch a much higher amperage circuit (load voltage). In the case of an ignition relay, the key/ignition switch is not capable of handling the high amperage requirements of the engine components electrical draw, so a relay is run in the circuit and controlled with the keyswitch. The relay has an electromagnet (control) and a switch (load) inside, and the electromagnet moves the switch when the control is energized. You do not ALWAYS have to have a burned fuse to have a bad relay, the contacts on the switch can burn, or the wire in the electromagnet can open, both resulting in a non-functioning relay.