I have a 2011 F150 Eco that I want to add extra LED lights to. I'm going to splice the lights into the current fog light wires so when the fog lights come on they will too. I just need to know what wire is positive and which is negative. One wire is grey and the other is grey with a yellow strip. Any ideas which is which?

 

Your multimeter can probably tell you....

 

Yellow stripe positive on mine but I would just verify with a multimeter.