Passing wires through the firewall - Jeep Cherokee Forum
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Passing wires through the firewall

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Old 07-07-2016, 07:47 PM   #1
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Default Passing wires through the firewall

So...done this more than a few times on other vehicles. Don't see an easy way on my XJ, feel like a dunce. Help this perpetual noob.

I have one amp power wire (8awg) and two wire harnesses with connectors (3/4" by 1/2") that I need to pass through on the passenger side. Can't find any existing spots to tap into. Figured I'd double check with y'all before making a new hole, maybe I'm missing something? If absolutely needed, I could always cut the connectors off and splice the wires together once they are passed.

Ideas, suggestions?


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Old 07-08-2016, 05:34 PM   #2
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Don't know of any good spots big enough to pass that through. If you are OK with re-soldering or re-crimping the wires, you could go with the firewall pass through that screws down onto the wires to make it waterproof.


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Old 07-08-2016, 06:18 PM   #3
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I've passed all of my wires through a grommet on the driver's side that dumps them out up above the pedals. You'll most likely have to cut the connectors off.
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Old 07-08-2016, 08:16 PM   #4
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I've passed all of my wires through a grommet on the driver's side that dumps them out up above the pedals. You'll most likely have to cut the connectors off.
its a huge grommet...there for the 5 speed vehicles...iirc, silver dollar size...the wires fit thru that, rtv up any hole you have.
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Old 07-08-2016, 08:47 PM   #5
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What in the world is a "one amp power wire (8awg)"?

I'm pretty sure you can run a lot more than 1 amp through an 8 AWG wire.
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Old 07-08-2016, 10:46 PM   #6
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Don't know of any good spots big enough to pass that through. If you are OK with re-soldering or re-crimping the wires, you could go with the firewall pass through that screws down onto the wires to make it waterproof.


I was thinking of a poor mans version, but I can probably score a couple of those from work.

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I've passed all of my wires through a grommet on the driver's side that dumps them out up above the pedals. You'll most likely have to cut the connectors off.
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its a huge grommet...there for the 5 speed vehicles...iirc, silver dollar size...the wires fit thru that, rtv up any hole you have.
Trying to stay on the passenger side, at least for the amp wire. That spot may work for the other wires. Thanks.

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What in the world is a "one amp power wire (8awg)"?

I'm pretty sure you can run a lot more than 1 amp through an 8 AWG wire.
Funny thing about the interwebz...hard to tell when someone is joking sometimes. Just to clarify...I have an audio amplifier power wire, 8 gauge...
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Old 07-08-2016, 11:13 PM   #7
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Passenger side is not ideal for any wire routing. Use that driver side grommet for everything and route from there.
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Old 07-09-2016, 03:07 AM   #8
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Passenger side is not ideal for any wire routing. Use that driver side grommet for everything and route from there.
This is correct. With the AC/Heater garbage in the way, your only real option is this. Although, you could run it through the grommet that the antenna wire goes through (located behind passenger side kick panel) and then run THAT through the passenger side inner fender.

I myself would personally stick with the gang of wires that runs through at the driver's side though - which is where I also ran mine.
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Old 07-09-2016, 07:55 AM   #9
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Funny thing about the interwebz...hard to tell when someone is joking sometimes. Just to clarify...I have an audio amplifier power wire, 8 gauge...
Funny thing about English. When you say, "one amp" and you are talking about power conductors, the usual meaning is amperes, not amplifier.

If you are running 8 AWG to power your amp, I strongly recommend that you run a ground wire of the same size to the battery terminal. Body grounds really aren't very good for large current loads. Without a dedicated ground wire, you are sharing the existing body ground with all the other electrical loads in the vehicle, and take at look at where and how it's attached to the battery. It's not exactly a great grounding point for an amplifier. No matter how good a grounding job you do at the amplifier, you are still going back to the battery via an inadequate grounding point.

If you are concerned about voltage drop by running the power the extra distance to the driver's side, you can always increase the size to compensate. What's the power output of your amplifier, and where are you planning to mount it?

What are you using to fuse the power?
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Old 07-09-2016, 10:50 AM   #10
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Funny thing about English. When you say, "one amp" and you are talking about power conductors, the usual meaning is amperes, not amplifier. If you are running 8 AWG to power your amp, I strongly recommend that you run a ground wire of the same size to the battery terminal. Body grounds really aren't very good for large current loads. Without a dedicated ground wire, you are sharing the existing body ground with all the other electrical loads in the vehicle, and take at look at where and how it's attached to the battery. It's not exactly a great grounding point for an amplifier. No matter how good a grounding job you do at the amplifier, you are still going back to the battery via an inadequate grounding point. If you are concerned about voltage drop by running the power the extra distance to the driver's side, you can always increase the size to compensate. What's the power output of your amplifier, and where are you planning to mount it? What are you using to fuse the power?
I've never heard someone say to run an amplifier ground back to the battery. My ground is about 6inches long to a seatbelt bolt and has functioned well for years.
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Old 07-09-2016, 10:56 AM   #11
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I've never heard someone say to run an amplifier ground back to the battery. My ground is about 6inches long to a seatbelt bolt and has functioned well for years.
Yep, you'll here me say it too-

Never, ever, run a high-draw device (amp, fan, E-brakes...etc...) off the chassis.

NEVER.

Always to the source.

Equal size wire.
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Old 07-09-2016, 11:01 AM   #12
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To answer the OP-

Pull down carpet from pass side firewall.

Drill 1/8" hole in the clear (both sides) high on the foot well from INSIDE out.

Use 1" hole saw (mini holesaw) to cut a hole for wires.........using your 1/8 pilot hole.

Get 1" grommet, slice from center out.

Run wires through hole.

Slide grommet over wires, insert grommet in hole.

Done.
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Old 07-09-2016, 03:26 PM   #13
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I've never heard someone say to run an amplifier ground back to the battery. My ground is about 6inches long to a seatbelt bolt and has functioned well for years.

Well, I guess you have never talked to a pro, then.

(There are a lot of idiots working in car audio shops. They are not pros. Actually, most of them are not.)
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Old 07-09-2016, 05:03 PM   #14
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Originally Posted by BlueRidgeMark View Post
Funny thing about English. When you say, "one amp" and you are talking about power conductors, the usual meaning is amperes, not amplifier.

If you are running 8 AWG to power your amp, I strongly recommend that you run a ground wire of the same size to the battery terminal...
Ah, touché on the wordplay As far as this next part...I have always ran the ground the shortest distance possible to a good body/frame connection. However, I am far from perfect and am always open to the idea that I have been doing something incorrectly all these years, so I looked into it. Both Crutchfield and Rockford Fosgate state that the ground should be a very short distance form the amplifier, RF goes one step further and specifies not to wire the ground all the way to the battery.
http://www.crutchfield.com/S-n6Y3M0t...ion_guide.html
http://www.rockfordfosgate.com/suppo...er/std_alp.php
With these two sources, I didn't think it was needed to search further.

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I've never heard someone say to run an amplifier ground back to the battery. My ground is about 6inches long to a seatbelt bolt and has functioned well for years.
Same here, shall we continue...
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To answer the OP-

Pull down carpet from pass side firewall.

Drill 1/8" hole in the clear (both sides) high on the foot well from INSIDE out.

Use 1" hole saw (mini holesaw) to cut a hole for wires.........using your 1/8 pilot hole.

Get 1" grommet, slice from center out.

Run wires through hole.

Slide grommet over wires, insert grommet in hole.

Done.
Exactly what the plan was if there wasn't a better way, so it shall be.

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Well, I guess you have never talked to a pro, then.

(There are a lot of idiots working in car audio shops. They are not pros. Actually, most of them are not.)
Now don't get me wrong, this may very well be true in a competition system, and may even have some sort of advantage in a larger power draw situation. But the two links I posted were from "pros" as far as I'm concerned and the amplifier I am running is roughly 300watts (had it forever, don't remember specifics).

If it's any consolation, I have been kicking around the idea of getting one of these sets of beefy battery/ground cables that are all the rage here.

And...back on topic...I am not running a wire from the front right, full left to the driver side, full right again to run down the passenger side, even with a bigger wire to compensate for lost draw. That is counterproductive. I do appreciate the I put though.


Edit: the RF link doesn't seem to be working, here's a screenshot from my phone; best I can do right now...


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Old 07-09-2016, 09:38 PM   #15
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The above pic-

Just above where you are considering coming through the fire wall.


When I wire my amp I will do as you are doing......however......regarding your post from Crutchfield...etc......RF interference.

I will bring amp pos cable to to the pos post on the small fuse block, neg wire will go to the neg post to the left, straight from the battery.

I have no concern for RF interference as I no longer use FM radio, streaming media is not effected by RF noise.

Wiring here is for all my accessories, light bars, e-brakes, trailer accessories, e-fan, ...etc....

I know where my grounds are.

I had a so-called pro wire the sound system in my last truck. He grounded amp to chassis and I had to clean ground several times....nothing by problems and will never again ground to chassis.

Last edited by Jeep Driver; 07-09-2016 at 09:48 PM.
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