Wiring in fog lights

Crux · May 20, 2016

I recent got a 2014 GMC Sierra 1500 which did not have fog lights. I got a set and have them installed in the bumper but have not wired them yet. What I want to do is have them wired to the headlights so when the headlights auto turn on/off the fog lights turn on/off also. Problem is I don't know what wire to tap into. The fog light kit I got has a switch and relay I still want to use in case I want to turn the fog lights off. Can anyone help me out with wiring suggestions?

Thomcat · May 20, 2016

Not as simple as tapping into a wire.

gen5diy.com makes a custom harness with integral relay(s) for aftermarket fog light installation. Worked fine on my Camaro. Have a version for the Sierra

http://www.gen5diy.com/GMC/Sierra/P-P-Harnesses7/Foglamp-Harness8/

Versions for both on or off with high beams depending upon State inspection requirements

Crux · May 21, 2016

I have a harness, looking for a power source. Was wanting to use the headlight wire as power.

Jdkno · May 22, 2016

Your not going to be able to use the headlight wire for power. You will use the headlight wire to power the relay, power for the fogs should come from the battery. What you will need to do is tap a headlight wire for the turn on lead for the relay, switch will go in line with that wire so you retain the ability to completely shut them down if you want to.

So if your working with a standard SPST relay: tap headlight wire run that to one leg of switch, from other leg of switch to relay pin 86. Power from battery + to pin 87 on relay, run the main power from the fogs to pin 30 on the relayear and ground relay pin 85. That's pretty much it, obviously the fogs will need to be grounded and if your switch is illuminated you would have a ground leg on that as well to deal with.