Running CB Coax through firewall

[RaisedByWolves]

I've read the threads I found via search but still don't have the answer I'm looking for.

Where's the best place to run a CB coax through the firewall?

I'm on the driver's side, and the small grommet where people cut the nipple isn't large enough to fit the coax male end even with the grommet fully removed.

I'm nervous to cut and feed it through the large (2.5"?) grommet that has the main wire housing because I believe it'd compromise the integrity of the waterproofing.

Is there another location?

Or do people drill their own hole and buy a grommet?

Or if you go through the 2.5" with a cut do you marine silicone after?

Thanks

 

[MeefZah]

You can get coax and a PL259 through the 2.5" grommet.

I have never used any sort of weatherproofing and I have yet to have an issue with coax and other power wiring passing through the 2.5" - this on 2 personal installations and one installation for a friend. I'm 3:0 so you should be good.

 

[proimion]

Why run coax through the firewall--front mounted antenna? What size coax? For some antennas, it can be real thin. Hopefully that is the case for you. I can't imagine running a thick coax through the firewall.

You've already answered your own questions--it is going to be tough. You've already discovered this and there is no magic.

You can see in my radio install I fed power through the firewall (not coax) and that was plenty hard enough. I wish I had gone through the driver's side in retrospect. I did run wire through the driver side for marker lights and that side was much easier.

I did cut a small slice in the rubber grommet and worked the cable through that. It was not easy. I thought about sealing it with silicone, but honestly, the fit was so tight I can't imagine water getting through. I don't go through water that deep anyway. You can't remove the entire grommet, either, as that would have water and noise repercussions.

You could also get a small section of narrow copper tube (or something similar) and force that through. Then feed the wire through that and then remove the tube. That would make it easier to get the wire through that grommet.

Have I mentioned this is not easy? Sorry!

 

[RaisedByWolves]

Thanks! Very helpful. I assumed this is what I'd have to do but wanted to be sure. This is the coax cable: https://www.amazon.com/RG-58A-Coaxial-Cable-Pl-259-Connectors/dp/B001JT0CGI

It's mounted on my gobi as a flip up/down.

Thanks again

 

[MeefZah]

Why run coax through the firewall--front mounted antenna? What size coax? For some antennas, it can be real thin. Hopefully that is the case for you. I can't imagine running a thick coax through the firewall.

You've already answered your own questions--it is going to be tough. You've already discovered this and there is no magic.

You can see in my radio install I fed power through the firewall (not coax) and that was plenty hard enough. I wish I had gone through the driver's side in retrospect. I did run wire through the driver side for marker lights and that side was much easier.

I did cut a small slice in the rubber grommet and worked the cable through that. It was not easy. I thought about sealing it with silicone, but honestly, the fit was so tight I can't imagine water getting through. I don't go through water that deep anyway. You can't remove the entire grommet, either, as that would have water and noise repercussions.

You could also get a small section of narrow copper tube (or something similar) and force that through. Then feed the wire through that and then remove the tube. That would make it easier to get the wire through that grommet.

Have I mentioned this is not easy? Sorry!

If it's not easy, you are doing it wrong.

OP, it's simple. Slit outer "skin" of grommet towards outside edge. Push knife in and slit inner liner underneath outer liner. Each slit should be big enough to cram your pinky through, tightly. Take a long zip tie. Push it through from the inside into the engine compartment. Tape your coax and connector to the side of the zip tie protruding into the engine comp. Lube the connector with water, Windex, spit, what have you. Pull other end of zip tie back into passenger compartment. Wiring comes with it. Done.

 

[e60ral]

Yeah, just tape it to something and it will pull straight through even with the connector. The drivers side is very easy, the passenger side is also easy but takes a little more caution that you don't damage the wire bundle because the access isn't as good.

You could put seal up your slit I guess but I would just leave a water trap on the wire (drop it lower than the slit before the slit so any moisture would drip off and not follow the cable inside). It doesn't need to be 100% waterproof, if you have water that high you've got a lot more problems than some water getting through that grommet.

 

[LOLSNOW]

Hope this gives you some ideas. I ran a pos and neg 4AWG wire in these locations. The negative required making the hole with grommet a little bigger. The positive wire I made my own hole using a step bit. Also these are sealed fittings that have a o ring that compress around the wire and even has a rubber gasket that compresses against the firewall for a water tight fit.

 

[mvt4r]

I've read the threads I found via search but still don't have the answer I'm looking for.

Where's the best place to run a CB coax through the firewall?

I'm on the driver's side, and the small grommet where people cut the nipple isn't large enough to fit the coax male end even with the grommet fully removed.

I'm nervous to cut and feed it through the large (2.5"?) grommet that has the main wire housing because I believe it'd compromise the integrity of the waterproofing.

Is there another location?

Or do people drill their own hole and buy a grommet?

Or if you go through the 2.5" with a cut do you marine silicone after?

Thanks

In addition to the alternate location, you shouldn't have to cut the grommet to get a wire through. It is very stretchy. In my Off Grid Engineering Second battery thread I used a straw, nail and some electrical tape to push the wire through a random location in the grommet.

The trick is the have a good taper to penetrate the grommet (it is very stretchy) and no shoulder along the path that will start to pull the grommet out of the hole instead of the wire in the hole (think a conical shape from point to wire).

One method that should work is to get a stiff pipe just big enough to fit the wire. Cut it at a steep angle and sharpen it to a point. That should be able to push through the grommet, then you can thread the wire through the pipe and retract the pipe.

Having said that, if the wire is 3/4" wide or something like that, this may not work so well.

Here is the relevant post from my thread.

 

[mvt4r]

Thanks! Very helpful. I assumed this is what I'd have to do but wanted to be sure. This is the coax cable: https://www.amazon.com/RG-58A-Coaxial-Cable-Pl-259-Connectors/dp/B001JT0CGI

It's mounted on my gobi as a flip up/down.

Thanks again

Yeah, getting that connector through is not going to be fun. Any ability to cut and recrimp one of the ends, probably the end inside the passenger compartment to retain the weather tight seal on the other end. That'll make things much easier.

 

[RaisedByWolves]

Thanks for the ideas all.

I'm going to create a slit near the top of the 2.5" grommet and slide the coax down to the bottom of the slit. I'll feed the wire/connector through to the inside. I'll make the grommet flush again and then put some silicone on the slit to provide a bit more sealing. The entire area is covered with mud from a recent run so I feel like this is cheap insurance.

Will report back.

 

[Landy]

You could also get a cable like this:

Wilson 305-830 18' Belden Coax Cable with PL-259/FME Connectors https://www.amazon.com/dp/B006NTK3MM/ref=cm_sw_r_cp_api_RO8xzbZ91ST25

Much easier to route and you attach the connector once everything is in place.

 

[MeefZah]

You guys are seriously overthinking this

 

[RaisedByWolves]

You guys are seriously overthinking this

Agreed

Cut a slit

Slid cable into slit so it didn't have to be as wide as connector.

Fed cable through

Did a dab of silicone over the slit

Good to go

 

[flyrv9]

Yea, either that or cut the connector off to reduce the size of the hole needed and then reterminate with a new connector easy peasy!

 

[Payara Offroad]

Hope this gives you some ideas. I ran a pos and neg 4AWG wire in these locations. The negative required making the hole with grommet a little bigger. The positive wire I made my own hole using a step bit. Also these are sealed fittings that have a o ring that compress around the wire and even has a rubber gasket that compresses against the firewall for a water tight fit.

Where do you find those fittings?

 

[Narat_524]

Where do you find those fittings?

They're called cable glands. Amazon.com has tons cheap.

 

[Boonedoggle]

Hope this gives you some ideas. I ran a pos and neg 4AWG wire in these locations. The negative required making the hole with grommet a little bigger. The positive wire I made my own hole using a step bit. Also these are sealed fittings that have a o ring that compress around the wire and even has a rubber gasket that compresses against the firewall for a water tight fit.

How did you get the one side of the grommet on non-engine side of the hole? Is that really accessible from the interior side of the wall?

 

[rageandlove]

How did you get the one side of the grommet on non-engine side of the hole? Is that really accessible from the interior side of the wall?

[MENTION=236368]Narat_524[/MENTION] - I'd love to know too as I haven't figured it out myself.

 

[Narat_524]

Yes, those areas are accessible above the steering shaft and pedals. Pull the kick panels, have a light small enough to fit but throws a flood beam, and you can see the areas on the interior side of the firewall.

Getting your hand on them can be another matter, but between poking holes in the steering grommet and drilling those two points, I have been able to run five different wires into the cabin. The cable glands are slick and clean, the steering grommet is down and dirty, but easy.

Steering grommet tip: Metal coat hanger, straighten it out, poke it through from engine side. In cab, bend coat hanger in a short "U" on the end, snuggle wire(s) up to U shape and electrical tape the hell out of it. Silicone spray or paste on tape. Pull back through from inside to engine bay. I suppose you could reverse those pull from engine to inside, but getting leverage from inside while bending the coat hanger is tough, as the dash gets in the way.

Narat

 

[rageandlove]

Thanks! I just need to run one wire (switch pros control) so I love the idea of a cable gland and having it really clean. Great tip. Appreciate it.

Yes, those areas are accessible above the steering shaft and pedals. Pull the kick panels, have a light small enough to fit but throws a flood beam, and you can see the areas on the interior side of the firewall.

Getting your hand on them can be another matter, but between poking holes in the steering grommet and drilling those two points, I have been able to run five different wires into the cabin. The cable glands are slick and clean, the steering grommet is down and dirty, but easy.

Steering grommet tip: Metal coat hanger, straighten it out, poke it through from engine side. In cab, bend coat hanger in a short "U" on the end, snuggle wire(s) up to U shape and electrical tape the hell out of it. Silicone spray or paste on tape. Pull back through from inside to engine bay. I suppose you could reverse those pull from engine to inside, but getting leverage from inside while bending the coat hanger is tough, as the dash gets in the way.

Narat