Ditch Lights & How to get through firewall

Hey there,

I have a 2020 TRD Off Road and I'm currently trying to wire up some baja designs s2 pros to a cali raised button on a switch panel I just got.

I've got the lights wired up to the battery + ground, and they turn on just fine with the supplied on/off switch.

I'm now trying to route this switch (which i will later cut and splice into the cali switch) into the cab, through the firewall.

All the tutorials I'm seeing say something along the lines of "just feed the wires through using a sturdy stick of some sort", however when looking at my firewall, it looks like there's a silicon (?) gel that is currently surrounding all the wires going into the firewall, blocking any air or moisture from going in.

I also noticed, from the inside cab side, there's a sort of plastic piece covering up the hole where the wires are coming through, making it very inaccessible to even grab a wire even if you were able to feed it through.

So, I'm wondering, are there any good ideas to get through the firewall if this coating is already there? I'm assuming I'm probably going to have to drill a hole and then feed the wires through, and then make sure that hole is sealed with something (what materials are good to seal it with?).

I was wondering if there were any other possibilities or smart options I might not have seen or thought of.

Here's some pics of the firewall, I tried to show the gel like substance however it was almost impossible to get a shot of it.

Firewall (the shiny part is the gel substance, hard to see, but it's there):

A further out shot:


From the inside with the plastic cone like thing blocking wires:

Any help or ideas would be great, I'm pretty new to this whole thing!

 

I went in through the flat rubber part of the grommet. Just taped the wires to a piece of wire coat hanger and pushed it through. Comes out in the floorboard above the footrest.

 

I was in your same position when wiring up a switch for my on board air. I used this grommet (see pic below) and punched a hole in the meaty center piece with a firewall wire insertion tool from O'Reillys. Set it down on a table you don't mind marring and push it through. It takes a lot of force so be careful with your fingers. Work your way around in a circle piercing it and you'll end up with a hole punched in it. Then you can feed your wires through and silicone the hole when you're done.

https://www.oreillyauto.com/detail/...rmance-tool-wire-insertion-tool/w2935/5344938

I had to use picks with increasing size to effectively stretch the firewall insulation on the other side of the grommet to get a hole large enough for wires to pass through. I envy the space you have down there to work with. It was a PITA to get the wires through with the clutch pedal in the way.

Hope this helped.

 

That plastic cone must be a new thing because I pulled 3 or 4 wires through that main grommet

 

From the Engine side beside where the hood release cable goes threw I used an old sharp paring knife to cut a slot in the gromet about an Inch long, then a long flat blade screwdriver, twisting it. that did the trick for me to route the RCA cable for the Front camera.

 

Assuming you are using a relay, there should only be a couple small wires to feed through. Use something like “Windex” as a lubricant to feed the wires through.

 

Do you happen to have a picture from the inside? I'm curious where exactly this comes out

 

I went through the lower one. It comes out near the fuse panel in the cab. I used a Phillips to get through haha

 

I was supplied a relay as a standalone cable which does have the black/white/blue wires that I've seen in a lot of videos - it also has a button to turn them on and off. What exactly is the relay used for? Sorry, I'm a noob at this stuff. The current setup has the wires connecting to each of the ditch lights, with those wires joining, which then attach to the positive battery terminal and ground. Then there's one button coming off of that which is used to turn them off/on. How exactly would a relay help this or affect this? Now I'm guessing if I'm even using the right cables for this project.

 

Most switches can't handle the current requirements of accessories like lights, compressors, etc. So the switch is used to control a relay that can handle the current load. The power for your lights should be coming from the battery, to an inline fuse, to the relay and out to the lights with the ground being the negative post on the battery. The switch is on a separate circuit that controls the relay. When the switch circuit is closed (switch turned on) it triggers the relay to close which sends power to your accessories. The switch circuit can be powered off the fuse panel under the dash with fuse taps. You can get those at your local auto parts store as well. They're nice because it's an easy, reversible tap for the switch circuit power. I can snap some pictures of the fuse panel with which ones I tapped into if you want to go that route. Just let me know.

 

I've done an add-a-fuse to wire in grille lights, so I'm familiar with that concept.

For the relay, interesting. I have two sets of cables which admittedly, I don't know which I should be using. One has a relay, one doesn't. Here's the one with the relay:


And here's the one currently installed:


This one (currently installed) has the inline fuse, but it doesn't have a relay. You can see the wires to ground/positive on the battery, and then when you flip the switch seen here:


The lights do turn on via the red button currently there, so I know they're at least working in some capacity. Does this seem incorrect then? I figured since they're working that I did it right but honestly I got these wires so long ago that I don't remember which ones actually came with the ditch lights.

I know I'm going to have to cut the wires (regardless of which harness I end up using) in order to wire it to a cali raised switch, however in all the videos and tutorials I see them using the wires from the harness with the relay which makes me think I should be using that.

Also, regarding the relay, can it just be mounted anywhere? I see there's a hole for a screw to go in but I don't know if it needs to be attached to ground or if it's just to be able to mount it out of the way. I assume the latter but just wanted to check.

 

I would use the one with the relay. It's a safer option so you aren't running all those amps into the cab with the switch only setup. It looks like thw switch only harness would work judging by the thickness of the wires going into it. But again, the relay one is safer and is more clean and easy for pulling wires into the cab for the switch. You pull smaller wire with the switch&relay setup as opposed to the switch only one.

That tab on the relay I assume is just for mounting, but it could be ground for the control circuit or lights circuit. There is a ground that goes to the battery on it so it should ground through there. You could always hook it up real quick and test it out with and without the relay mounted to a ground spot. That'll tell you if the mount is just a mount or if it doubles as the ground for part of the circuit. If it doesn't work when the relay isn't mounted to a ground, it needs a spot with ground. But if it works when it isn't mounted to ground, it can be mounted/zip tied anywhere.

 

Great. Thanks for the help, I really appreciate it. I'm going to go ahead and swap out the wires for the one with the relay and test them as you suggested.

Thanks again!

 

No problem!

If you have more questions, just shoot!

 

I'm using that same grommet there to wire two sets of light wiring from engine bay to cab. Best spot IMO.

 

S2 Pro draw 1.7a each, so you are just barely over the 3a CH4x4 style (cali as well) switch limit.

Better to use the relay and breathe easy.

I would go through that grommet where everyone else does. Sounds like maybe there is new stuff on the ‘20, but it shouldn’t stop you. There are other plugs as well.

 

Always use a relay when powering lights. As others have pointed out, the current draw might be more than the switch can handle. You don't want melting wires under your dash. Well, you don't want them anywhere, but particularly somewhere that you won't know what's going on until too it's too late.

The relay will have at last four terminals. One will be for the hot side of the wire powering the lights. Another will be for the switched side of the wire powering the lights. The hot side goes to your power source through a fuse. Put the fuse as close to your power source (presumably the batter) as possible. Then there is a powered wire to trigger the relay. That is the one that will go into the cab and to the switch. Call that the "control" wire. The last wire is a thin black wire to ground the relay.

When you switch the lights on, the control wire goes hot and activates the relay. Power goes through the relay and powers the lights. You should be able to pick up the power for the switch from the fuse block under the dash. That will simplify your installation and you'll only have to run one wire through the firewall.

This is a typical relay used in automotive applications.



30 comes from the power source/battery.
85 is the coil ground.
86 is the coil hot (control) wire. It can go to any suitable power source.
87 will be for the switched wire that goes to the lights.

Ignore 87A, it's used for situations where you want power on when the switch is in the off position. Most relays have 87A, but some don't.

When I'm doing wiring, I usually start from the device and work back to the power source. The very last step is connecting the hot wire to the power source.

I hope that helps.