Passing wires through the firewall - Jeep Cherokee Forum

Go Back  Jeep Cherokee Forum > Technical Discussion > Aftermarket electrical systems
Passing wires through the firewall >

Passing wires through the firewall

Aftermarket electrical systems Aftermarket electronics only! stereo head units, CD players, MP3 players, speaker systems, amplifiers, hardmounted GPS devices, computers, headlight upgrades, fog lights, off-road lights, general wiring and anti-theft devices.

Passing wires through the firewall

Reply

 
 
 
Old 07-07-2016, 06:47 PM
  #1  
CF Veteran
Thread Starter
 
jay_sco's Avatar
 
Join Date: Dec 2011
Location: IE (SoCal)
Posts: 1,074
Year: 1994 SE
Model: Cherokee
Engine: 4.0
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?


jay_sco is offline  
Reply With Quote
Old 07-08-2016, 04:34 PM
  #2  
Junior Member
 
Ad-HocXJ's Avatar
 
Join Date: Jul 2015
Location: Maryland
Posts: 87
Year: 1993
Model: Cherokee
Engine: 2.5L MFI
Default

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.


Ad-HocXJ is offline  
Reply With Quote
Old 07-08-2016, 05:18 PM
  #3  
CF Veteran
 
XJlimitedx99's Avatar
 
Join Date: Jul 2012
Location: Milford, NH
Posts: 2,362
Year: 1999
Model: Cherokee
Engine: 4.0l
Default

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.
XJlimitedx99 is offline  
Reply With Quote
Old 07-08-2016, 07:16 PM
  #4  
Senior Member
 
rzldzl's Avatar
 
Join Date: Dec 2012
Location: cariboo, bc
Posts: 559
Model: Cherokee
Default

Originally Posted by XJlimitedx99 View Post
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.
rzldzl is offline  
Reply With Quote
Old 07-08-2016, 07:47 PM
  #5  
CF Veteran
 
Join Date: May 2012
Location: Lost in the wilds of Virginia
Posts: 4,335
Year: 1994 (parting out) and 1998 Classic (under restoration)
Model: Cherokee (XJ)
Engine: 4.0
Default

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.
BlueRidgeMark is offline  
Reply With Quote
Old 07-08-2016, 09:46 PM
  #6  
CF Veteran
Thread Starter
 
jay_sco's Avatar
 
Join Date: Dec 2011
Location: IE (SoCal)
Posts: 1,074
Year: 1994 SE
Model: Cherokee
Engine: 4.0
Default

Originally Posted by Ad-HocXJ View Post
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.

Originally Posted by XJlimitedx99 View Post
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.
Originally Posted by rzldzl View Post
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.

Originally Posted by BlueRidgeMark View Post
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...
jay_sco is offline  
Reply With Quote
Old 07-08-2016, 10:13 PM
  #7  
CF Veteran
 
thatXJguy's Avatar
 
Join Date: Jul 2012
Location: Hudson, FL
Posts: 3,682
Year: 1999
Model: Cherokee
Engine: 4.0L Inline 6
Default

Passenger side is not ideal for any wire routing. Use that driver side grommet for everything and route from there.
thatXJguy is offline  
Reply With Quote
Old 07-09-2016, 02:07 AM
  #8  
Someone stole my badge!
 
Basslicks's Avatar
 
Join Date: Mar 2011
Location: Ocala, FL
Posts: 11,137
Year: 1992
Engine: 4.0 HO
Default

Originally Posted by thatXJguy View Post
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.
Basslicks is offline  
Reply With Quote
Old 07-09-2016, 06:55 AM
  #9  
CF Veteran
 
Join Date: May 2012
Location: Lost in the wilds of Virginia
Posts: 4,335
Year: 1994 (parting out) and 1998 Classic (under restoration)
Model: Cherokee (XJ)
Engine: 4.0
Default

Originally Posted by jay_sco View Post
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?
BlueRidgeMark is offline  
Reply With Quote
Old 07-09-2016, 09:50 AM
  #10  
CF Veteran
 
XJlimitedx99's Avatar
 
Join Date: Jul 2012
Location: Milford, NH
Posts: 2,362
Year: 1999
Model: Cherokee
Engine: 4.0l
Default

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. 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.
XJlimitedx99 is offline  
Reply With Quote
Old 07-09-2016, 09:56 AM
  #11  
Banned
 
Join Date: Jan 2014
Posts: 1,054
Model: Cherokee
Default

Originally Posted by XJlimitedx99 View Post
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.
Jeep Driver is offline  
Reply With Quote
Old 07-09-2016, 10:01 AM
  #12  
Banned
 
Join Date: Jan 2014
Posts: 1,054
Model: Cherokee
Default

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.
Jeep Driver is offline  
Reply With Quote
Old 07-09-2016, 02:26 PM
  #13  
CF Veteran
 
Join Date: May 2012
Location: Lost in the wilds of Virginia
Posts: 4,335
Year: 1994 (parting out) and 1998 Classic (under restoration)
Model: Cherokee (XJ)
Engine: 4.0
Default

Originally Posted by XJlimitedx99 View Post
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.)
BlueRidgeMark is offline  
Reply With Quote
Old 07-09-2016, 04:03 PM
  #14  
CF Veteran
Thread Starter
 
jay_sco's Avatar
 
Join Date: Dec 2011
Location: IE (SoCal)
Posts: 1,074
Year: 1994 SE
Model: Cherokee
Engine: 4.0
Default

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.

Originally Posted by XJlimitedx99 View Post
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...
Originally Posted by Jeep Driver View Post
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.

Originally Posted by BlueRidgeMark View Post
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...


Last edited by jay_sco; 07-09-2016 at 06:21 PM.
jay_sco is offline  
Reply With Quote
Old 07-09-2016, 08:38 PM
  #15  
Banned
 
Join Date: Jan 2014
Posts: 1,054
Model: Cherokee
Default





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 08:48 PM.
Jeep Driver is offline  
Reply With Quote

Thread Tools
Search this Thread
Quick Reply: Passing wires through the firewall


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: