I am trying to find out if the headlghts on my '03 has negative side switched headlights. I am in my local volunteer fire department and am trying to wire in a wig wag flasher for my headlights. I am getting voltage to all three wires at the headlights when the brights are on. From what I have found, this means I do have a ground side switch. Can anyone please help confirm this?

 

Yes, anything built after 02 should ground controlled evrything.