Fog lamp issue

[Duaine Reynolds]

2006 2500hd with factory fog lamps. Bought the truck without the fog lamp switch and no relay. I have put in 3 switches with no fog lights illuminating. Is the relay required? From what I've read, the relay is to auto-illuminate when dims are on. 

[Formulabruce]

The relay keeps the fog lights from working on High beams. They only work on low beams.

[Duaine Reynolds]

Thanks, I'll pick up a relay tomorrow.