Auxiliary Backup Lights

ChevMech · September 21, 2014

Last year when I purchased my 20x7 utility trailer, I put two LED lights on the front facing back to light the deck when I was forced to work at night and to double as back-up lights. On my 2003 Silverado, I just ran wire from the inside fuse panel, out the firewall, and to the trailer backup light fuse, with a toggle switch and a relay in their respective places, to make the lights work.

Let's move on to January. I bought a 2009 2500 HD Silverado LTZ (I mention LTZ because I know the dash boards differ). I connected the aforementioned LED lights to the factory trailer backup light plug on my 7-way. The lights work great now as they come on anytime the reverse lights are on. I really want to connect the lights so I can have them on even when the truck is not running. I'm thinking about running the wiring like I did before, but I'm curious if there is another way.

I'm not sure what GM was thinking when they built these things, but you can't turn the key to the "run" position and put the shifter into reverse and the backup lights stay on....it has to be actually running.

8.1HD/ALLISON · September 21, 2014

Here is my setup on my dump trailer. I hooked from positive battery supply to exterior weatherproof switch and then from switch to reverse circuit on trailer. Now with either reverse or flip of switch you have lights.

14GFXSilverado · September 22, 2014

The 7-way plug has an Aux 12v postion (1 o'clock postion when looking in the plug) This wire is live all the time and is fused. If you connect your lights positive wire into the 7-way plug then you will always have power when plugged into the truck. I have a mobile rv repair business and this is how I have one of my trailers wired. Works great.

ChevMech · September 22, 2014

Thanks guys for your suggestions. I'm taking both into consideration. What I'm looking to have everything controlled from the driver's seat. Is there an easy way to make that 12V lead switchable?

8.1HD/ALLISON · September 23, 2014

You could trace wire from fuse panel and cut and wire switch in the cab.

14GFXSilverado · September 23, 2014

Yes this can easily be done. as 8.1HD said just go into the fuse box under the hood and locate the stud that feeds the 12v power to the plug. undo the wire and run a new wire from the stud into the cab to a switch. then from the switch run another wire back to the original wire that was connected to the stud. this will then give you control of the 12v aux feed to the 7-way plug and would still use the original factory fuse. install time would be roughly 15-20 min tops.

Ianf · September 23, 2014

I like the idea of using the stud in the fuse box, but, use a relay and switch instead so you aren't running 40Amps live into the cab around all that sensitive electronics. You'll also be able to control the feed to the trailer aux. anytime you like. If there is a battery in the trailer for a dump or other electrics, they will not work unless the switch is turned on giving you control of the drain on the main battery.

ChevMech · September 23, 2014

Thanks again guys for you help!!! I had it wired that way similarly on my old truck, but I didn't want to mess something up by doing that on this new one.

I'll gather the supplies and try to have this done by the end of the week.

Now for my next question on the project: Where is the best place to run wires through the firewall? I'm not fond of the idea of cutting wires in any vehicle. In the next few months I'm going to add some wiring for led running lights up front as well.

I know the new trucks push more power to the auxiliary plug when the truck is in tow/haul mode. Does this affect that in any way?

14GFXSilverado · September 24, 2014

ChevMech. As far as running a wire through the fire wall I always find a spot where wires have already been run in and have the rubber grommet in place. Usually you can just push a wire through the same harness. If im not able to to that then I will drill a hole in the firewall and install a grommet to protect the wire from rubbing and shorting out.

Another last minute comment is that you can always install an isolator to help protect the battery drain on the truck. The isolator will then only turn the power on when the key is in the accessory or on position.

The trucks actually dont put more power to the plug when in tow/haul mode. The voltage is only based on the output from the alternator. The higher the revs the more the output that is the only thing. We have tested this in my shop. So no it wont affect your output in anyway and the line is still only rated for the fuse you have installed... max 40amp.

good luck

ChevMech · October 30, 2014

It took me a couple of weeks, but I finally go my lights working how I wanted to. First of all, I bought some things they call "fuse taps". Interesting invention I must say. I tapped the fuse for the trailer back-up lights. From there I ran the wire to a toggle switch. My power is coming from and auxiliary fuse under the dash that I tapped into. I put a 20 amp inline fuse at the fuse box so I'm protected there.

This configuration had some unintended consequences. When I flip the switch no only do the trailer lights come one, the truck back-up lights come on as well. That will definitely make it easier to hook up a trailer in the dark.....and maybe freak some people out in traffic as well