Need Advice, Power Wire through Firewall?

[David Paul]

I installed my DrawTite hitch yesterday and have almost all of the trailer wiring completed except..........................

Got to the interior firewall and cannot find a place to thread the power wire through to the battery.

This is the 5th trailer wiring that I have installed over the years and have never been as baffled as I am with my 2018 CX-5.

Mazda really has this vehicle buttoned up tight. Usually there is an unused rubber plug somewhere but for the life of me, I don't know where it is or even if one exists.

Any advice will be greatly appreciated.

 

[Chris_Top_Her]

On the gen1's the pass through is on the upper left corner (maybe right) above the gas/brake pedals.. there is a rubber grommet where the wiring harness goes through.

 

[David Paul]

On the gen1's the pass through is on the upper left corner (maybe right) above the gas/brake pedals.. there is a rubber grommet where the wiring harness goes through.

Thanks for responding.

I saw that and apparently the Gen 2 is the same. However, it is apparently very thick. I tried to penetrate it with a heavy duty coat hanger wire to no avail.

I may try it again tomorrow after I grind a sharp point on the end of it.

 

[Chris_Top_Her]

careful not to nick a wire

 

[David Paul]

For sure. I was extremely careful when I was prodding that area.

My puncture efforts were aimed more to the side of the rubber grommet which is why the rubber is so thick there. Was staying as far away from the wire bundle as possible.

In the past, about half of my trailer wiring efforts were running the power wire under the car. This time, I wanted to keep the wire inside for a neater and safer install.

I should have taken it along the underside of the vehicle. Would have made my job so much easier. There is a large, unused plastic plug, that gives direct access to the undercarriage at the back end of the cargo area on the floor. I used that access to run my trailer hook up pigtail to the hitch.

Oh well, I'll eventually get it figured out. At least the Hitch is installed and the trailer lights wiring is about 90% complete.

 

[tibimakai]

When I have run my amp wire, I have used one of these(not exactly this one though):
http://www.evwest.com/catalog/product_info.php?products_id=431

 

[Mazdiod2]

Does anybody have experience running a wire through the firewall gasket? How big a wire can fit? Which direction is easiest?

 

[goodpeoples]

I ran 4AWG a few weekends ago. It was a pain, but I basically poked a hole into the rubber and used a knife to cut a cross section. After that, fed the power wire through. Cross section wasn't that big, so it took a lot more muscle to yank the power wire into the cabin. Coat hanger and vise grips will help the job.

Note, I did slice the grommet flaps on the interior open a lil more to be able to use my vise grips.

 

[Mazdiod2]

When I look behind the battery I can see a bundle of wires inside a rubber corrugated sheath which is connected to a big round rubber gasket. I'm guessing that is the correct one. I can't see very well behind the dash.
Did you start on the outside and work it in?
Did you poke the hole near the center, or the edge?

 

[goodpeoples]

When I look behind the battery I can see a bundle of wires inside a rubber corrugated sheath which is connected to a big round rubber gasket. I'm guessing that is the correct one. I can't see very well behind the dash.
Did you start on the outside and work it in?
Did you poke the hole near the center, or the edge?

I started from the outside. Not gonna lie, it took a lil time. Sucker's darn near air tight afterwards. I used a screwdriver to jam into the hole while I cutting the "X." Honestly, this was definitely an impromptu decision. I would say I poked the hole about a quarter inch away from the bundles of wires.

If I had to do it over again, I would actually poke the SAME distance, but lower, in reference to the bundles. The higher the hole is, the more difficult it will be to get to it on the inside. Like others say, be VERY careful not to stab the wire bundle. If we were looking at the grommet from the engine bay, I'd say to poke bottom left. In turn, viewing the grommet from the inside, the wire should be on the bottom right.

 

[Mazdiod2]

The bundle looks like about an inch around. The gasket is about 3". About how big is the hole on the inside? How about the actual hole in the metal firewall. Can you see it from the inside?

 

[goodpeoples]

If you go under your dashboard, there's this little circular flap. lift it up and you'll see the the gasket from the inside.

 

[Mazdiod2]

I'm wondering if this is the best way, although it looks like there is only one wire bundle that passes through the firewall.
There are those AC pipes going through but that might be even more trouble.

 

[theblooms]

I haven't looked at my CX-5 yet, but in the past on other Mazda's, if it has an automatic transmission just look for the spot where the clutch would have gone through the firewall. There's generally an unused plug there, so that makes a perfect spot to punch through.

 

[Mazdiod2]

I have the 6MT so that hole might be used. I haven't looked at it closely. It's kind of hard to see behind the engine.
If it's possible maybe I can feed the wires through there.

 

[murky]

For others, the Canadian OEM harness doesn't require running a power wire and doesn't pierce any insulation.

 

[goodpeoples]

I have the 6MT so that hole might be used. I haven't looked at it closely. It's kind of hard to see behind the engine.
If it's possible maybe I can feed the wires through there.

Then my advice does not apply..... You can route it via outside the CX-5 though. There's a video from e trailers I believe that shows this method.

 

[Mazdiod2]

I will be looking carefully when it warms up a bit.
I want to have a SAE charge point for the battery without lifting the hood, and I might mount a small 110v inverter under the dash alongside.
I have already run a wire under the vehicle for the hitch wiring.

 

[Mazdiod2]

I removed the battery and ran a 16ga pair through the big gasket.

There is a molding ( nipple) protruding around the top side in the engine compartment. I clipped it off with some angle clippers.

I slit the tape holding the two halves of the rubber around the bundle on the inside, under the dash. Then I could see light from the engine compartment through the hole. I has to enlarge the opening, making an 'x' with an exacto knife.

Then I was able to pull the wires though using a stiff wire taped to the 16ga pair.

 

[dave-who]

My 2019 CX-5 automatic has a stamped area on the firewall exactly where a clutch rod would go if it was a manual. It would require drilling a hole and the installation of a grommet. For that reason I'll be going under the car with my trailer lighting wire. I'll post photos later.