Convince Me I'm Nuts: Access Thru Firewall

[Mark Doiron]

EDIT: THE POSSIBLE SOLUTION DESCRIBED BELOW MAY PROVE USEFUL TO AUTO OWNERS AFTER ALL. SO, PLEASE IGNORE MY FIRST COMMENT HERE:

Right off the bat, let's just admit that you 95% of Gladiator owners who drive an auto may be able to just skip this thread. You have a great access where the clutch pedal goes for us minority who prefer to row our own gears. But, you may want to read the last paragraph and see if that applies to you. In which case, you'll probably want to take a look at the rest of this post.

I've been skulking around JT and JL forums and not been particularly happy with the solutions I'm finding for routing wiring from inside the passenger cabin to outside. I do occasionally ford rivers, so water-tightness is important to me. Simply being stuck in deep water requiring assistance could lead to a flooded interior if water can seep slowly in. So, poking holes through impossible to access points like the large rubber grommet behind the the glove box, or the drain plug over the fuel tank, are not particularly good. Not for me, anyway (though I have used that drain plug for the ARB compressor under the passenger seat).

Anyway, I've been searching for something better--even if it means drilling holes. So, I have an idea here and wonder if anyone else has tried this and learned (perhaps the hard way) that it is not a good idea. The idea is to pull off the end piece on the driver's side dash console. And to pull off the cowl corner piece on the driver's side (this may work on passenger side--I'll let someone else check that out, LOL). I'm thinking drill holes through each of the two panels that form the firewall--they appear about 1-1/2 to 2 inches apart. Make the holes large enough for rubber grommets. Feed the wiring/cable through, then seal with RTV.

A few photos that may help with understanding. The "Reference Panel Fastener" is just a visual guide to the same location from two different perspectives. ...

Appreciate folk's thoughts and/or experience with this.

While I'm elated with the aux switch package that Jeep offers, I'm really disappointed with the lack of easy access for firewall pass-through. The JK has two easily used points on either side of the passenger compartment. I'm thinking of giving this proposal a go. I may lay the windshield down and see if that improves access, though I think probably not. If anyone out there has theirs down right now, please take a look and maybe even post up a photo of what you see looking down into the area where I'll be drilling.

And for you auto drivers (also), if you've stuck with me this far: Routing RF cabling hither and thither is not a terribly great idea. The RF can get into other wires and cause signals that are misinterpreted by the associated system, causing some truly weird problems. I saw one friend in Moab where every time he talked over his CB, his third taillight would modulate off and on. And the other systems can create noise that is picked up by the radio receiver or by the mic audio line to create receive or transmit noise. Another friend of mine has a weird and loud sweeping noise in his CB receiver any time he runs his inverter. Normally you want to make wiring routes direct, and avoid coupling them with other wires (by running them together--zip ties are not your friend). Sometimes it's unavoidable, but it's best to do the best you can.
Anyway, appreciate everyone's thoughts.

Sponsored

 

[ShadowsPapa]

If you have seen the CAN-bus wires associated with OBDII you know they are twisted pair network wires. I recall a company where they were running out of capacity in the floor channels for network and telephone cables, so the night crew decided to run a print sharing setup over cables along the telephone route.
My crew got a complaint that every time "Jane's" phone would ring, the printer would spew out a few dozen pages of garbage........... the ring signal in the phone line introduced garbage into the network cable to the print sharing devices.

We ran IBM cable through one of the skywalks one weekend and got 3/4 of the way from one building to another - and a couple of the guys let the cable kink. Pull it out, toss it, start over........... it was critical that the wires run exactly as made- xx numbers of twists per inch, no interruption, no kink or bend.
Electrical current through wires produces an electromagnetic field around said wire.
Introduce the current such as turning on a light or activating a winch or whatever, the field grows around the wire - cut that power and the field collapses. Suddenly, and with more energy induced into the parallel wire.

It's why you never want to be neat and tidy when running your ignition wires- these guys that redo the engine bay and like their plug wires to be pretty and parallel and then gripe about misfires........ DUH. Cross 'em. Don't run them parallel.
Anyway, never run power wires near the vehicle's network wires. The CAN-bus wires are twisted pair for a reason - sensitive network protocol travelling along those wires VERY susceptible to interference from power wires.
If your RF wires, like CB antenna and such, are well shielded, END TO END, grounded on both ends, you should be fine but I'd still avoid the CAN-bus wires as much as possible- at least don't run wires parallel and neat and tidy. Don't coil wires, crossing is fine, cross over or over and back helps negate any induced current in the other wires.

When it's necessary to run things in close proximity - CROSS the wires, don't run them parallel.

 

[Mark Doiron]

If you have seen the CAN-bus wires associated with OBDII you know they are twisted pair network wires. I recall a company where they were running out of capacity in the floor channels for network and telephone cables, so the night crew decided to run a print sharing setup over cables along the telephone route.
My crew got a complaint that every time "Jane's" phone would ring, the printer would spew out a few dozen pages of garbage........... the ring signal in the phone line introduced garbage into the network cable to the print sharing devices....

LOL. Yeah, I've been on the troubleshooting end of tales like that. 27-1/2 years USAF avionics. There's the story about the EC-130E (which in later years I'd serve as flight crew on--4500 flying hours as in-flight avionics tech) that some autopilot fellow was installing a time compliance tech order and needed a ground wire. So he tied it off to the shield of our automatic direction finding equipment. It took us six months to figure out why that ADF wasn't working. Then there was the B-52 that the wing commander wanted to send to SAC Bombing Competition: Only USAF B-52 still flying with a MIG kill--red star painted on the nose was pretty cool. Except its radar nav was horribly unreliable. Pressure was really on us to get it fixed. Turned out to be someone had stepped on a waveguide, slightly cracking it internally. No visible damage outside, but it sure screwed up the accuracy of the bombing runs.

 

[smlobx]

Mark I think it might work but I have no idea what is sandwiched between the metal pieces. I’m sure you have probably thought of this but you should use grommets on both pieces and could use some butyl or silicone to fully waterproof the hole.
Keep us posted.

 

[ShadowsPapa]

If you use butyl or even urethane, to seal, make sure you won't need to pull it back out. It will be not only water-proof but theft resistant.
I use urethane to set door glass back in the "shoe" or bracket when the old original stuff comes loose.
Butyl was use to seal earlier car windshields in place.
Takes an act of congress to get that stuff loose (if you can wait that long)
smlobx's suggestion will seal if for sure. Even at a a few dozen feet under water.

 

[sad85XD]

Right off the bat, let's just admit that you 95% of Gladiator owners who drive an auto may be able to just skip this thread. You have a great access where the clutch pedal goes for us minority who prefer to row our own gears. But, you may want to read the last paragraph and see if that applies to you. In which case, you'll probably want to take a look at the rest of this post.

I've been skulking around JT and JL forums and not been particularly happy with the solutions I'm finding for routing wiring from inside the passenger cabin to outside. I do occasionally ford rivers, so water-tightness is important to me. Simply being stuck in deep water requiring assistance could lead to a flooded interior if water can seep slowly in. So, poking holes through impossible to access points like the large rubber grommet behind the the glove box, or the drain plug over the fuel tank, are not particularly good. Not for me, anyway (though I have used that drain plug for the ARB compressor under the passenger seat).

Anyway, I've been searching for something better--even if it means drilling holes. So, I have an idea here and wonder if anyone else has tried this and learned (perhaps the hard way) that it is not a good idea. The idea is to pull off the end piece on the driver's side dash console. And to pull off the cowl corner piece on the driver's side (this may work on passenger side--I'll let someone else check that out, LOL). I'm thinking drill holes through each of the two panels that form the firewall--they appear about 1-1/2 to 2 inches apart. Make the holes large enough for rubber grommets. Feed the wiring/cable through, then seal with RTV.

A few photos that may help with understanding. The "Reference Panel Fastener" is just a visual guide to the same location from two different perspectives. ...

Appreciate folk's thoughts and/or experience with this.

While I'm elated with the aux switch package that Jeep offers, I'm really disappointed with the lack of easy access for firewall pass-through. The JK has two easily used points on either side of the passenger compartment. I'm thinking of giving this proposal a go. I may lay the windshield down and see if that improves access, though I think probably not. If anyone out there has theirs down right now, please take a look and maybe even post up a photo of what you see looking down into the area where I'll be drilling.

And for you auto drivers (also), if you've stuck with me this far: Routing RF cabling hither and thither is not a terribly great idea. The RF can get into other wires and cause signals that are misinterpreted by the associated system, causing some truly weird problems. I saw one friend in Moab where every time he talked over his CB, his third taillight would modulate off and on. And the other systems can create noise that is picked up by the radio receiver or by the mic audio line to create receive or transmit noise. Another friend of mine has a weird and loud sweeping noise in his CB receiver any time he runs his inverter. Normally you want to make wiring routes direct, and avoid coupling them with other wires (by running them together--zip ties are not your friend). Sometimes it's unavoidable, but it's best to do the best you can.
Anyway, appreciate everyone's thoughts.

OK so fair warning, most of this is way above my head, may be a dumb question. (AUTO drivers.... I know )

But, is the "drain plug over the fuel tank" the ones on the driver/passenger floor? because theres also 2 holes that go out the bottom of the car.

 

[Mark Doiron]

OK so fair warning, most of this is way above my head, may be a dumb question. (AUTO drivers.... I know )

But, is the "drain plug over the fuel tank" the ones on the driver/passenger floor? because theres also 2 holes that go out the bottom of the car.

Yes, that's the one. It happens to be right next to where a half inch wire loom from the compressor originates. Where are the two holes to which you refer? Also, bear in mind that this time I'm routing RF cable--the shorter the route the likelihood of improved radio performance and reduced possibility of the types of interference I described in my first post. The cable will originate at the roof between the driver and passenger, headed for an NMO adapter adjacent to the cowl corner piece I showed in my original post. Going out the bottom is a bit convoluted. I have a soft top, so any solution that provides for mounting the antenna on the roof is a non-player.

 

[Mark Doiron]

If you use butyl or even urethane, to seal, make sure you won't need to pull it back out. It will be not only water-proof but theft resistant.
I use urethane to set door glass back in the "shoe" or bracket when the old original stuff comes loose.
Butyl was use to seal earlier car windshields in place.
Takes an act of congress to get that stuff loose (if you can wait that long)
smlobx's suggestion will seal if for sure. Even at a a few dozen feet under water.

I normally use RTV sealant (what most folks call silicone sealant). We always called it RTV in my military days (room temperature vulcanizing).

 

[JimThe4th]

So here's a crazy thought. Why even go inside the passenger compartment. If you are starting just below the soft top you could run it down the side of the windshield. That tube sticking out of the lower windshield is the drain hole for the header bar. if you fold down the windshield you could just run the RF cable down the A-pillar.

 

[Mark Doiron]

So here's a crazy thought. Why even go inside the passenger compartment. If you are starting just below the soft top you could run it down the side of the windshield. That tube sticking out of the lower windshield is the drain hole for the header bar. if you fold down the windshield you could just run the RF cable down the A-pillar.

Thank you! As I wrote above, we do plan to have a look with the windshield folded down. That should happen tomorrow. And that sounds like a perfect solution.

 

[JimThe4th]

quick image of a JL with the windshield folded down. Tie off points are limited, but there is ample room for an RF cable, especially if you are using something thin like RG316

 

[Mark Doiron]

Got the windshield folded down yesterday. It looks like I'll be able to route cable around the fixed windshield frame, and then under a piece of rubber seal at the bottom driver's corner where another cable and the drain hose are located. Few pics that may prove useful for others interested in this area ...

About a ten minute job. Most difficult part was pulling the wipers off their studs. They were pretty stuck ...

Checking out if I can hide cable from outside view along the fixed windshield frame ...

The mesh loom was a test for physical space where I'd route the coax. Didn't have a piece of coax handy at my friend's shop (It was pouring rain outside, where I'd be working if at my house, LOL) ...

Windshield folded down. Ditto the above comment about the mesh loom ...

RF cable will then be tucked between the fixed windshield frame and the plastic trim, then routed through the box at the center holding the adaptive cruise control hardware, then onto the molle rack with the radios (you can see the mics hanging down at the center of the image) ...

 

[Mark Doiron]

Alright, started off cool this morning, but no wind. So, decided to wrap up this radio antenna install (note that the nice shop photos you see are a friend's business, not mine to use everyday, sadly). Anyway, did end up using the lowered windshield to route the cable, but not by drilling any holes. As was suggested by Jimthe4th, that proved unnecessary. I routed around the windshield frame, which was easily accessible with the windshield lowered. Since I was routing between the front driver's cowl and the overhead molle rack, there was little else needed. A few pictures for those of you wondering how you might use this. I tested only the CB antenna, and after a bit of shaving of the length had a 1.0:1 SWR on my antenna analyzer on channel 4. I think that's a bit optimistic (i have many decades measuring SWR as a avionics tech in USAF and you don't ever see 1.0:1--there's always reflected power), but am still quite pleased with the results.

Open hood and mount antenna bracket. It attaches to an existing screw. On the Rubis, you have to use the last one back because of less clearance with the raised fenders. There are four holes if you want an additional screw (one is supplied with the bracket). I wanted, but none of the four holes lined up very well with the underlying sheetmetal. So, I drilled another one and used the supplied screw to provide a security blanket for me.

Next, pull the cowl end piece. It's held on by four T45 screws (you got the tool with your Jeep toolkit). Pull those and then pull the plastic cowl piece outboard (not up). Then lower the windshield. 10 minute job, instructions are with that tool kit. Note that I found it easier to pull the windshield wiper blades by turning them at a right angle from the motor stud, then gently working them off. Route the cabling along the accessible space under that cowl end piece. I used a 1/4" Adel clamp on an existing screw to hold it in place. Note the 1/4" diameter aluminum tubing on the cable. I placed that to relieve the pressure of the windshield gasketing when it's raised. This may prove to be a problem in wet weather--at least I'll know where to look first if I have any water intrusion. This is RG-58 cable; my tubing would not have fit over RG-8X, which I'd have preferred to use because I have crimp tools and SO-239 connectors for it. But it's slightly larger than the RG-58..

Route coax up the windshield frame. I used stick-on zip-tie holders. If you place them carefully (inspect the windshield as it's raised before placing each one), you can avoid contact with the drain line and wiring on the windshield itself while keeping your new coax out of sight once the windshield is raised. It may turn out that these stick-on devices lose their grip in the heat. I'll take care of that should it happen. Next, tuck the cable between the fixed windshield frame and the plastic covering.

There are two small gaps on the back side of the windshield frame that I used for the power wires (that red shrinkwrap in the background) and the new coax cable (center far left--wrapped in what-I-call F-4 tape from my years of USAF service). Poke a heavy wire (I used 12 gauge) through that toward the front of the vehicle. Once you work it out the front, tape it securely to your new coax, then use that to pull the coax through. From there I used a couple more Adel clamps to secure the coax, then trimmed the length and soldered an SO-239 connector to the end of it. That will attach to the output of whichever radio I wish to use for a particular trip.

By using an NMO mount, I am able to quickly swap the antenna between the ham, CB and GMRS radio bands.

Delighted with the way this came out. Now, a bit of positive real world experience to back up the implementation and I'll be super happy. Note that the antenna bracket comes from Topsy Products. The NMO mount comes from Laird, and includes 17 feet of RG-58, but no connector. I think you all can figure out sources for zip-ties, zip-tie mounts, aluminum tubing, SO-239 connector. Because antennas use NMO, which is a widely used industry standard, you have a lot of choices. I won't even begin to tell you what particular flavor you should prefer, but I will tell you that one very popular company has published misleading info that illustrates they don't have a clue how cable length for radio antennas is determined, so I do avoid them. Hint: Cable length should be as short as possible, the only exception being if you're attempting to run multiple antennas (like truckers you see with two antennas, one on each mirror). Good luck if you decide to replicate this install!

 

[WhatExit?]

FYI: Here's a link to my CB installation thread which details how i mounted the antenna and ran the cable through the firewall and to the glovebox:

https://www.jeepgladiatorforum.com/...enna-installation-in-my-jeep-gladiator.27639/

 

[Mark Doiron]

FYI: Here's a link to my CB installation thread which details how i mounted the antenna and ran the cable through the firewall and to the glovebox:

https://www.jeepgladiatorforum.com/...enna-installation-in-my-jeep-gladiator.27639/

I'm going to assume that firewall plug you pulled for access on the driver's side is for the clutch pedal. That wouldn't work for me.

Sponsored