I will finally be hooking up my off road lights on my roof in a few weeks. I have been researching and looking at other threads in regards to getting through the firewall. See the attached photo... is drilling a hole in that spot still the best way to get into the cab from under the hood? For the wiring to get from the roof to the engine I plan to take the exterior a-pillar off and put the wires underneath it, then reattach the a-pillar panel over top. If anyone has done something similar could you be kind enough to upload photos of how you successfully ran your wires (both from the roof to the engine, and from the engine through the firewall)? Thanks!

 

I'm not sure drilling there was ever a "best" way. Seems like that would be a hard spot to get at as you are going to be down behind the engine there.

The "factory" dealer installed off road lights have the wires run through the factory wiring harness point on the firewall up higher and toward the outside. You can see it from under the hood near the brake booster.

As far as getting wires to the roof. I think those are generally pulled from the inside and poked through the grommet in the top corner roof light and then sealed up with silicone.

 

I had planned on running my wires down the A-pillar externally and under the hood the way this guy did: for the same reason he explains, his marker light grommet leaked and he already siliconed it shut

Here are the photos from another hummer forums thread on how to get wires through the firewall... is it easier to get the wires through the factory grommet instead of drilling a new hole? I'd have to look to see where it is located from...

If any one has a better/easier way I would greatly appreciate it if you could add some photos to this thread

 

I have a massive bundle of wires which I ran through the firewall. I just made a slice through the inner and outer rubber grommets of the factory harness running through the firewall. It's towards the upper left when looking under the driver side dash. You'll see a big factory harness running through the firewall.


It is a pain to force a big bundle through those grommets but I didn't want to drill.

 

Stooooppp .. Seriously stop . Dont drill or try to run anything thru the main wiring grommet. ..
I tried and mess my truck big time .
While trying to run a wire for ligths not sure what I did but nothing works. Error messages on display for engine . Transmission and tranfer cases .
The truck didnt want to start

To make the story short . It cost. Me +2000 plus . Between tow , dealer and rent cars .after truck.was fixed I take it to a truck Accessory shop . They charge me around 200 for a profesional install on both lights roof and bummper . They Also fix all the mess I had from previous wiring
once you cant run the wire is
Not worth to mess with electricity
Trust me on this one . IM a do it yourself guy

 

Can you elaborate further? How did you mess up your electronics? Did you accidentally cut your oem wiring harness? I've run wires thru the factory grommet on my wife's escalade and didn't have any issues. Did you do the wiring wrong? The harnesses I bought are pretty plug and play, not sure how I could mess up the electronics setting it up. I paid to have the lights installed in my H3 but looking at it afterwards, it didn't seem that difficult. My biggest issue is that I don't feel like I trust someone at a truck accessory place to not damage the interior of my H2 where parts are hard to come by

 

There was a few acc wires already going thru the firewall grommet . I thought it would be an easy task but since it was the first time I didn't know how to do it. Drilled a small hole on the groomet I used a stick wire to fish the wire I need to pass.
Somehow. Not sure if the drilling or can't explain how the stick tangled with some of the truck wiring. While pulling back
It ended doing a mess cutting one or two wires
The truck was crazy. I got errors such Tranfer case need service . A few codes .the engine start for a few sec then shut off
The lights didn't work.
A totally nightmare.

Identify which wires were cut took the mechanic a few hours .
I do everything in my truck but realized that electrical is not my thing.
Also the shop did such a great job . Even match the switch with the oem . They fix my previous hid install . And some wires for the amp . All for $200ish .

On the other hand maybe I wasn't careful enough.

 

I have I would imagine close to a 3/4" of wiring running through the factory grommets next to the factory harness without issue. I wouldn't say I was overly careful when going through the grommets but I also stayed towards the outer edge of the grommets, away from the factory harness. I also did not drill the rubber but made slits with a new razor on the inside and outside grommets to help the wiring pass through.


It is definitely doable, just have to be careful.

 

Yes, I would say that one should NOT attempt to drill through the factory harness grommet ever, under any circumstances with anything even resembling a drill or anything particularly sharp. I have poked wires through mine in both my GMC truck (pretty much identical harness and grommet location) and my H2 without any issue. I recommend staying toward the outer edges of it as LoJac mentioned. I have always used a quite long philips head screwdriver to poke the whole through it and then tape the wires to the end of the screwdriver and pull it back through with the wires.

If you do this and feel some sort of undue resistance or feel at all like something might not be right then just stop and try again.

 

It seems like drilling a new hole and going thru the factory grommet both have their pros and cons. I'm heavily leaning toward the factory grommet becuz I am not positive the switch wire is long enough to go the other way thru the area I'd have to drill from and reach. See the X's on the attached photos, my game plan is to slice thru that area, then run a metal coat hanger thru to feed the wires using electrical tape. Is that similar to what you did? Thanks!