can i wire a switch into this light?

[happyjourney]

i have to have relays on the headlight?

 

[loquin]

i have to have relays on the headlight?

If you're going to be using an auto style headlight (55 W,) you certainly should.

the bulb will pull over 4 amps after it has warmed up, and a LOT more than that when it's initially turned on.

(Tungsten, the filament material in most bulbs, has a positive temperature coefficient of resistance, meaning that, as temperature goes up, so does the resistance in the wire.) Initially, when the filament is cold, the resistance is very low, and the current is correspondingly high. Since, when you switch it on, the current draw is very high, it would fry your switch after not many times of switching it on.

A relay is designed to switch heavier loads, and it only needs a small current to the coil to energize it. This saves your switch contacts.