I'm still new here and might have placed this in the wrong forum. If so, I hope an admin will move it to its proper place. I didn't put it in a forum based on the year model of my F150 because I think it is a question applicable to most all models.

My '90 F150 4.9L straight drive just doesn't produce enough light for safely backing up. I found a pair of reasonably priced and powerful auxillary LED lamps that I plan to mount beneath the rear bumper angled slightly outward (5-10°). I've never done this before and don't want to create a wiring problem. I don't want them switched separately but want them to come on when the stock back up lights are switched on with lights on and placed in reverse. I watched a YouTube that only confused me further because it involved splicing into hot wire feeding the stock back up light, then adding a relay, fuse, and power wire all the way back up front and connected directly to the positive battery terminal and finally a common ground from the relay to the chassis. That seems to me to be a shotgun for a gnat.

Can anyone tell how to do this and why or point me to a wiki, youtube or how-to article? Is a relay really needed? If so, why? Does the sub-circuit to the relay need to be fused? If so, why? Does 12V power really need to be taken from the battery? If so, why? If not, what other sources to power the relay should be considered?

I searched here but didn't find one on the subject.

TIA

 

First step I did was this

These were a big improvement over stock, but it got to be at the barely usable point and I wanted more
So the next step was this
That got to the wife seal of approval.

Now in my truck, I had led pods under the bumper first, but wanted something cleaner.
So I did this

Flush mount sr-q lights and rear power port
Now to answer your question
Why a relay..
The backup light circuit is meant for small drawing bulbs, not a larger current draw. So the relay uses a small current to act as a trigger to open the contacts to a power supply that can handle the load.

 

I added the brightest led bulbs to the original backup lights. This helped. Then I added rock climbing lights to the back and side. Am happy with the results. Also added the rock climbers to the front side and tied those to the driving lights for more light on the side.

 

Great job!!!!

Thanks for the post!