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"How To" run power cable through the firewall no new holes

119K views 36 replies 22 participants last post by  Onlyina_Chevy  
#1 Ā·
hi everyone. this is my first time post.i have looked through this site a lot.

well im installing a new sound system in my 09 silverado .with the new system i dont want to make any major cuts or holes in my truck. so my challenge is to install a great sounding system with out major surgery.i know im not the only guy looking to do this.so here is one of my first but more to come post on installing different parts into the gmt900 body style. this is just the power wire
i will post more as i go on other post.

1. first off im going to reuse most of my old sound system that came off my other car. so it gives a new meaning to recycling .

i have 1/0 gauge cable that i need to feed into the cab. as you can see its about 3/4 inch thick round.
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after looking around for a day . the area behind the fuse block has a large grommet that all the wires feed into the cab. it is very flexible so it will allow this big wire into the cab with out having to make a new hole . i must warn you will need lube to push a big cable into this rubber grommet. you can use electrical lube they sell at home depot. or ky jelly if thats all you have. haha that is the same stuff that the electrical lube is. well it looks like it. but trust me it makes the job way easier . make sure you have towels hand cause once the lubed cable starts to come into the truck your hands wont be able to get a good grip to pull.
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the best way to do this if from the engine side into the cab. i tried from the cab to the engine for an hour with no luck. i used some angled needle nose pliers to slide the opening of the rubber grommet open and then started to feed the cable in. went right in . oh by the way there is a lot of electrical tape you have to remove before you can get to the rubber grommet. i also found it was way easier if you remove the fuse block but make sure you disconnect the battery first.
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once you lift up on the gray handles it will start to disconnect but some of them are very stubborn dont just yank on them. take your time and work them out. this is what is under the fuses
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those harnesses are also held into place with plastic clips on the sides. carefully remove them and all harnesses will be out of the way so you can remove the plastic tray 3 bolts should be holding it down.
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once all that is out of the way it gives you all the room you need to do the job.
look at how the 1/0 gauge cable fits into the factory rubber grommet. no new holes drilled into the firewall.
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then i taped it back up with electrical tape just like gm factory did
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here you get better view of it all. the other thing i did not like at all . is the way chevy ran the trailer light and power wires to the fuse block. they look cheesy. they run along the sides of the fuse block so i will take care of that since i have it all apart
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so i ran the wires under the fuse block . there is plenty of room with no dangers of pinching the wires
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putting it back together you can see the trailer power wires under the block
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with the fuse block back on the trailer wires installed
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no wires hanging down the side like some after thought
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with cover
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with wire loom now it looks like it should
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for now this is where i hooked up the power. it will change if i need to but i will see how it works out.
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over all view yes there is an inline fuse
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now this is with the wire look installed and the wire secured to the wall.
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on the inside of the cab the wire comes in right behind the fuse block. one you get the wire in it helps to have someone to help you push the wire while you get it to turn down once that is done just pull what you need keep the wire with lube. there is plenty of room back there.
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i ran it down the drivers side
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from there they go to the rear behind the seats. its a crew cab. im going to work on my amp rack .i will also upgrade my ground to 1/0 gauge .
that all for now.
hope this helps out some people looking to run there power wire with out making wholes in there fire wall. not to mention hide the trailer power wires.
 
#3 Ā·
you dont have to take apart the dash .but it does help . you just have to remove the lower part on the drivers side there are 2 phillips screws and a 10 mm bolt that holds down the e brake release . once you remove those it pulls out towards the drivers seat. it has clips holding it in.
 
#4 Ā·
by the way .
im not a professional audio installer. just a old guy that loves a good sound system and love to do his own work on his truck and cars.
the setup you see now is just temporary where the fuse sits and also all the power wires from battery and grounds will all be upgraded.just wanted to get some diy pics up on getting the wire into the cab. i do plan on adding an extra battery and a high output alternator .

i also just happen to find out that my fuse should be 15 inches or less from battery. oops
oh well by the time im done with it all im sure it will all be done correctly.
 
#7 Ā·
Looks great, thanks for the write up. I'm going to attempt the same thing in a week or too after I have finished my sound deadning. Would it be possible to fit two runs of 1ga in there? Looks like a tight fit with even one. Another thing' do you think I could get away with not removing the fuse box? Seems like a ton of extra work to me.
 
#8 Ā·
darren700 said:
Looks great, thanks for the write up. I'm going to attempt the same thing in a week or too after I have finished my sound deadning. Would it be possible to fit two runs of 1ga in there? Looks like a tight fit with even one. Another thing' do you think I could get away with not removing the fuse box? Seems like a ton of extra work to me.
yes it can be done with out removing the box.
but i will let you know that your sight will be limited due to the box being in the way . all so your space to be able to get 2 hands to work is very limited because of the fuse box. to tape things back up after you set every thing up is next to impossible. it will take you less time to take apart the fuse box than to cut strips of electrical tape to try to wrap the grommet. i originally started doing this with out removing the box. if i would have know i would have just removed it before starting. i got the wire in and did the pull with the box still in. but finishing it up was where i found myself removing the box to have access to taping up the line.

the main hole in the fire wall can take another one of the 1/0 gauge cables. but i dont know if you can get 2 of them in the opening of that grommet ?
i could have just punched a hole on the top of the grommet and just pushed the cable into the cab. but it would not be as nice. besides that i dont know how it would affect the grommet in the long run. say 10 years from now
good luck let me us know if you got 2 of them in.
 
#9 Ā·
oK, will post once ive finished and let you guys know, but i probably wont get to it for another week.
I have a feeling your right and i may need to cut the side of the grommet to get the second wire in. When you took out the fuse box did all the fuses stay in place in the top plastic piece or did you have to take them out individually?
 
#10 Ā·
darren700 said:
oK, will post once ive finished and let you guys know, but i probably wont get to it for another week.
I have a feeling your right and i may need to cut the side of the grommet to get the second wire in. When you took out the fuse box did all the fuses stay in place in the top plastic piece or did you have to take them out individually?
they all stay in place . the top piece comes out with the fuses all as one. its a tight fit so take your time it will all work out in one . so dont worry about removing each fuse. they all stay in.
 
#11 Ā·
I finally got around to running my two 1ga power wires today.
I didnt remove the whole fuse box, only the cover and the panel holding the fuses, that gave me enough room to get the job done.

The grommet inlet looked like it had no extra room so i just cut a X shape higher up on the outer grommet. I put three layers of electrical tape, a layer of duct tape and another 2 layers of electrical tape on-top, hopefully thats enough.

For the inner grommet, rather then cutting it i just pulled out the top corner and ran the wire out the side. I figured the otter grommet is completely sealed so i could get away with this on the inside rather than slicing it. there was no room to get a knife in there anyways. I then ran the wire under the middle of the seat, since theres no way 2 runs of 1ga would fit on the side like the original poster did.

thanks for your advice it really helped! here's some pics. (yes i did sound deaden the entire floor and back wall, still debating on whether its worth the effort to do the roof).

enjoy the pics.
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#13 Ā·
Love the how to, but trying to push several small wires and a couple pneumatic lines through it, I gave up and just punched a hole through it on the side with a screwdriver and ran the lines that way, still water tight and ended up being a lot easier to do. A little silicone will help seal anything.
 
#14 Ā·
deathphoenix99 said:
Love the how to, but trying to push several small wires and a couple pneumatic lines through it, I gave up and just punched a hole through it on the side with a screwdriver and ran the lines that way, still water tight and ended up being a lot easier to do. A little silicone will help seal anything.
Yea, pushing is hard and your method is likely just as good, but FWIW:

I found it easier to push a stiff fish tape through, tape my bundle of lines to the fish tape, and pull through.
 
#17 Ā·
LAD42DER said:
Has anyone drilled their own hole and installed their own gromet. I had a bad experience with running wires with the vehicles main harness so I am trying to avoid that. Pics would be great too
i'll take a picture in the morning and show where my two locations are....that factory harness has data wires that are 22 gauge and are FRAGILE...just a stress fracture is enough to stop the truck from starting...therefore i stay clear of that main harness

the first location is less than a foot away from that grommet

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the other location is on the passenger side floor board...theres a plastic 2" plug you can drill...i wouldnt recommend anything larger than 4 gauge on this side though...but from the plug you can run between the truck the the body mount then behind the inner fender and come out right behind the battery
 
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#19 Ā·
I tried this method and no matter what I tried, could not get through that inner grommet. I ultimately gave up, taped it back up and decided I'll try again next week. Anyone have any tips of how to get the wire through that pesky inner grommet?
 
#20 Ā·
I have to run a simple camera wire through that grommet. Sounds like that might be harder to do than the 1 gauge wire. I thought I had found my answer after reading this thread until I got to the later replies of others trying to get smaller wires through. I don't want to have to puncture the rubber grommet if at all possible. Has anyone else had success with getting a small wire through without puncturing the grommet or without taking the fuseblock and half the engine bay apart?
 
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#21 Ā·
murkedout said:
i'll take a picture in the morning and show where my two locations are....that factory harness has data wires that are 22 gauge and are FRAGILE...just a stress fracture is enough to stop the truck from starting...therefore i stay clear of that main harness

the first location is less than a foot away from that grommet

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Can you take a picture of the firewall where you drilled through on the inside? I'd like to see just to get an idea of where to drill. Seems like having a second grommeted hole going into the cab would be a fine idea in case I decide to add more runs in the future. Thanks!
 
#22 Ā·
"in case you decide to add more runs in the future???" Me thinks you better use a 1" or bigger drill. It all starts with one, pretty soon you are running wires by the handful. Hahaha, good luck. An extra grommet in the firewall done at the factory would have been an easy thing to add, but I am guessing that GM doesn't want to encourage a lot of electrical mods to their vehicles due to warranty issues with after market electrical components.
 
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#23 Ā·
^^^^^^^ that's funny but true. About gm and aftermarket electronics. I prefer to use a grommet from aamp of America or stinger ask your local stereo shop guys they should know who they are (wholesale only) it's called a pro grommet. You drill the hole one piece goes inside and then the plastic nut attaches to it and it seals water tight. Used when I ran 0 gauge worked great in my Tahoe.
 
#24 Ā·
There's a decent selection of pro grommets on eBay, but it's a little overkill for what I'm currently doing. I'll be more running the handful of wires than single large diameter power feeds. Right now I just need to run a couple pairs of speaker wire and a couple pairs of 10-12 gauge power wire. That being said, I'm sure I'll find something that needs more power in the future!
 
#26 Ā·
Being a mechanic, I would be weary about putting more pressure on an already pulled tight main harness. In theory it probably wouldn't hurt anything. But if you nic a wire, you could create a lot of issues. On the other hand, drilling already rust prone vehicles might not be your thing. I dropped my wire on my 2012 LT straight down the inside wheel well, got a firewall gromet, and ran the wire up the bottom of the right side of the cab and in through the plastic plug under the right side rear seat. I used silicone RTV to seal the firewall gromet and ran 3/8" conduit from the battery to the gromet. Using zipties to secure it to the body. This also gave me a good look at my frame, which needs to be cleaned up. The North East eats these vehicles.I ran it under the carpet, made a couple slits in the carpet where the cables come out to Amp in the center of the truck under the rear seat. It was the easiest install in a long time.
 
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