Whats up everyone. I just bought a sick 99 GMC Sierra :metal: . Truck has the works, but thats another thread and I'll get some pics. It has some large driving lights behind the grille that are hooked up onto the factory foglight switch. When on highbeam you cant turn the driving lights on. I was wondering if anyone knows if there is a way or how to interphase the two so in times of much needed light you can run both hi and driving lights at the same time?

I'm also going to be doing the mod to run both low and hi at the same time when his are activated as well. Can never have too much light.

Thanks for all the help in advance. Keep on truckin :metal:

Obviously this isn't a perfect answer, but give's some general info. I've done this on one domestic vehicle and one foreign. Both times it was finding the fog light relay and either eliminating it and using a heavy gauge jumper wire (10-12ga) or opening the relay and internally modifying it so it was jumpered. This would allow the fogs to run when the highs were on.

Whats up everyone. I just bought a sick 99 GMC Sierra :metal: . Truck has the works, but thats another thread and I'll get some pics. It has some large driving lights behind the grille that are hooked up onto the factory foglight switch. When on highbeam you cant turn the driving lights on. I was wondering if anyone knows if there is a way or how to interphase the two so in times of much needed light you can run both hi and driving lights at the same time?

From what I gather you have aftermarket driving lights behind the grill that are switched with the factory fog lights. If this is how it is, you have a decision to make. It sounds like the fog lights are currently switched on from the driving lights. You need to find this “switched” relay wire for the driving lights and connect it to the high beam of your truck. This way when you have on your high beams your driving lights will come on with them. However, this WILL NOT affect the fog lights, they will function the same as they do now. If you want to make the factory fog lights stay on all the time, that is a different story. You have to manipulate the factory wiring for that. Like another post said, I think there are aftermarket harnesses that will allow you to make it happen. Hope this helps.

Hopefully you would only do this offroad, I know the bright lights on those trucks are bright anyway. Plus, some states only allow you to run 4 white lights to the front of the vehicle at any given time while on the roadway, which when your bright lights are on, all four of the headlights are on. Just wanted to mention the legality, courtesy side of it.

don't quote me, but I have been told that fed regulations dictate the aux lights are supposed to go off when the high beams come on.

I believe that is a regulation for manufacturers. To my knowledge not illegal unless you blind oncoming traffic.

That may well be true bob... I know i read it somewhere , but didn't even think about it only being for the builder.
Now the question is, how come the builder can't do it... but the owner can?