Help! Wire routing question for aux driving lts.

[alstep]

Hey guys..fairly new to the forum, and I'm hoping someone here can help me..2012 Explorer XLT, and I am installing a set of PIAA driving lights, and being an electrician by trade, am fine with all the wiring/ relay, ect., in itself..But NOT being a mechanic (lol) I am trying to figure out the best way to route my switchleg from inside the cab to the engine compartment where I am mounting the relay..I literally only need one wire, as the switch can be grounded right inside the cab as well, and I am feeding it from a switched 12V pwr source in the cab as well. Anyone ever try this, i.e. feeding a wire through the stock wiring bundle that goes through the firewall? Any ideas? I'd rather not drill any holes if I don't have to_pretty tight in there! Thanks for any ideas

 

[Anime]

Welcome to the site.

In newer vehicles, it can be tough to find a pass-through point, since most of the wires are often bundled together tightly, wrapped with multiple layers of tape, and apparently stuck to the large rubber firewall grommet they go through.

Sometimes you can use an awl or sharp pick between the wiring and the grommet to make a tiny space to get a wire through, but you need to be careful since you can also puncture the grommet instead. Some people do intentionally puncture the grommet when passing larger wires through, then seal up the hole with RTV silicone.

You can also use the old trick of sticking something like a coathanger or other metal rod through, taping the wire to it, then pulling it back through. Again, care needs to be taken not to puncture or tear the grommet when doing this.

You might also look around the firewall for the smaller grommets, there's usually one or two other wiring pass-through points and the smaller ones might have more space or just be easier to get to.

One other possibility is to find the factory wires that aren't being used. Lots of newer vehicles have many unused wires, with empty harness plugs under the dash for optional equipment that particular trim level didn't get. Even if there aren't empty harnesses, there are usually a few wires that aren't actually connected, but this can be tough to tell, even with a wiring diagram, unless you know for sure what a wire is for and that your vehicle doesn't have whatever it would operate.

You can of course tap into these wires on either end, extending as needed.

Just take your time and find a good spot, you should be able to sneak a small gauge wire for a relay through.

 

[Melon]

I had enough room at the hood latch cable grommet that I could run the 2 wires through there. Not sure of it will work on your 2012, but it did on my 2000.

 

[NickyB]

Fire walls suck...

I have a 2016 and the design of our vehicles are fairly similar. A lot of people will say look at the Police Interceptor schematics and it will get you through. For me that didn't work at all. I got through my fire wall by piercing through the grommet which houses the hood opener. It was a major pain in the ass. Had to remove trim on the interior and take out the battery. Granted that's not very hard, getting your body in the right angles is lol. Follow the hood release, poke through from the engine into the cab, stick a flashlight in there to see the light, pull it through, and hope you don't pull the grommet through like I did. My bundle of wires was much thicker than yours would probably be though.

 

[Mike65]

On my 2000 Ranger there is a grommet by the door hinges on both sides of the truck, I removed it & drilled a hole in it then reinstalled it & ran the aux light wires from inside the cab to out behind the fender to under the hood to the relay. On our 99 Sport there is a rubber boot covering the wires from the power door locks, mirrors, & windows, you could carefully put a small cut in the boot & run your wires from inside the truck into the boot then out through the cut you made in the boot & then behind the fender into the engine compartment. Here is a pic of how I did it on my 2000 Ranger.