I will be hooking up glow guages sometime this weekend. I drive with my fogs on all the time, even during the day. So my question is, how do i hook up the guages if i only want it to turn on when the actual headlights are on.

I have rewired fogs

 

just when the headlights are on? not with the parking lights on too? go to the headlight relay and use that output as a trigger for the guage relay (you may have to add one)

 

you wont have to use another realy just tap in the headlight wire or run it off the fuse for the headlights