I am looking for anyone who has done this and trying to figure a few things out. How did you get your amp hot wire through the firewall? The amp I am running uses 4 awg wire. I am planning on tapping into the rear door speakers for input to my powered line out converter. I would like to put everything under the back seat. I am a 20 year electronics tech but I also like to find the best way to wire this before I start cutting into my carpet. Any advice?

 

Hoo doggy. 4 AWG?!?! That's in the neighborhood of 100 amps, or about 1200 watts. Is that what the amp actually needs?

That's a pretty fat wire.

 

That's in the neighborhood of 60 amps @ 500W RMS, my power cable run is approximately 18-19 feet. Length = resistance, which = voltage drop, which = the need for a 4awg cable. This is going into a Supercrew and needs to run from the battery to the back of the cab on the opposite side. Too small a cable is bad, too big a cable will never hurt.

 

Getting through the firewall is very difficult with these trucks, and you can forget trying to sneak a new wire alongside the harness bundle going through near the steering column. But if you run under the cab, it is easy to get into the cab via the rear wall.


Bring the passenger side rear seat back forward and remove the jack. Then remove either one or two of those plastic retainers and from the bottom, lift the material that covers the rear wall. It is black and kind of stiff. Behind there you will find a vent with a very thin mesh over it. I have brought several antenna and power wires into my cab that way. That vent allows air flow out of the cab when all the windows are closed.


It is very hard to access from outside the cab because Ford how has several rubber strips between the cab and the bed. They may be for airflow or soundproofing, I'm not sure. So run a stiff wire (a messenger wire) from the inside through the vent hole and down towards the ground. Then attach your new 4 awg wire and pull it into the cab.


Good luck.

 

Thanks David, I have wired audio equipment in many vehicles. After having a cursory look yesterday I am thinking your suggestion is the way to go. It looks like there may be a firewall plug on the passenger side lower and to the right than the wire bundle pass-thru but when I look under the dash inside I cannot find it. I took apart everything I could. I might even be able to go through the driver side but there does no appear to be a way to route it from the battery side to the drivers side (under the hood) that would professional and not "rigged". I would love to keep that 4 AWG wire under the hood and inside the cab. Thanks for your advice.

 

Just did my 2015 f150 super crew. There is a big grommet on the drivers side where there is a little nipple on top of the big grommet. Just clip the top of that nipple off and run your wire through there and down the threshold. Plenty of room for big wire if you really want that. There is also one on the passenger side but its hard to get to from the inside. Just go down the drivers side. Super easy. I ran mine in about 10 mins.