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Stop Your Trailer

7183 Views 7 Replies 6 Participants Last post by  knaffie

This is a semi-brief overview of what it takes to put a brake controller into a tow rig. I'll start with a typical hard wire set-up, where you have to run all of your stuff from finding power to wiring the plug. After that, I'll start into factory tow package stuff.

Everything I'm going to outline here is assuming nothing is trick about your tow rig, and nobody has gotten creative with the wiring. If you decide to take on this project and have any questions, feel free to ask. I'll try and answer the best I can.

A hardwire brake controller

First things first, look around the back of your rig and find out if you have wires run from the factory to run lights. If your rig has them, they could be wrapped up around each other and tucked up out of the way. Most times it is easy to spot them. Suburban's have them up under the drivers rear fender, and Ford's and the newer Chevy's have them wrapped up and taped to a wire loom behind the bumper... You get the idea. If you and I can't find them, you could probably stop by a hitch place and have them take a look. Some rigs need to have a T-connector, and others may have a plug that you can pull your wires from, or plug a harness into. I found a really good link while doing a little research on this where you can get most of any tow rig parts. While you are there, pick up the female connection you need to plug your trailer into. This link will also give you some different options as to how to mount the plug.

Go down to your local auto parts place and pick up a couple of self resetting circuit breakers. Get one 20 amp and one 30 amp.

Pick up 25 or 30 feet of blue 12 guage wire, 30 or 35 feet of black 10 gauge wire, a 10 feet of white 12 guage wire. That should be more than enough wire, but it's better to have too much than not enough.

You need a couple of electrical ring terminals too. You need five #10 ring connectors for 10-12 guage wire (the yellow ones). Decide where you are gonna pull your power from. Different trucks have different places to pull power from, and any given truck has several different places to do that. You need to find out where you are going to do that, and get any terminal you will need to fit over the stud that has power. Could be at the battery, at the starter, or from the feed on a buss bar. You also need a couple of blue butt connectors, a couple yellow butt connectors, and maybe a couple of different sized scotch locks. Unless the controller you buy comes with one, you will need at least one blue one. Zip ties, black tape, and split loom also make the job a little cleaner. Go ahead and pick up a small assortment of other electrical terminals just to have them on hand if you find a place where one would work better than another. Pick up a couple of 1/4" self tapping screws, and a box of #10 self tapping screws, to mount stuff and attach grounds. The ones with the hex head work best in a cordless drill.

Find someplace under the hood to mount the circuit breakers. You want them to be as close to power as you can get. Under the hood of these late model trucks can be really crowded, so good luck, you may need to be creative. Use a couple of #10 screws to attach them to something. Watch and make sure that you don't punch through anything important, and that nothing is going to smash the breakers when the hood is shut.

On the circuit breakers, there should be two different color posts. One silver, and one brass. If they are the same color, they should be marked 'Batt' (the brass post) and 'Aux'(the silver post). 'Batt' is the power side, and 'Aux' runs to the controller or the plug. Strip the ends off of a chunk of black wire long enough to go between the brass posts on the breakers. Attach a #10 ring terminal to each end and put them on those posts.

Run the black and blue wires up from the back of the truck. Don't worry about making them permenant yet, but run them how they are going to be strung, i.e.: over, around, and through crossmembers and brackets. Pull those wires all the way up under the hood. Pull the black wire up to the 30 amp breaker and attach it with a ring terminal. Pull the blue wire up and feed it through the firewall. I usually can find a grommet already in the firewall that I can fish the wire through. Sometimes it is neccessary to drill. If you have to drill, look at where you are going to drill through, and what is on the back side of the firewall. It will ruin your day if you drill through the firewall, and tag the fuse box, or if you go the other direction and punch the brake booster. Leave enough slack up under the hood that you can pull more wire through if you need it.

Mount the controller under the dash. I usually mount them down low and to the right. That keeps it down out of the way but still accessible to make adjustments and reach the manual slide lever. Mounting down low also makes it easier to remove the controller without the screw holes showing. When you finally trade your pig in on that new hi-po diesel whatever you have been saving your pennies for, you will get a better trade if your dash isn't all torn up. Other people that tow often like to move the controller up closer to within reach. The manual control lever will save your ass if you ever tow in conditions that are less that ideal. If you save your road trips for more fair wether, you won't have to worry as much.

Pull the blue wire up and connect it to the brake output wire coming from the controller (usually blue). Leave enough slack so that you can route those wires up and out of the way when you are finishing this job up.

Now you can worry about making the wires under the truck permanent. Start at the firewall, and work your way back down the truck. Stick a handful of zip ties in your pocket and go to town. I try and tie the wires right to the wiring that already runs down the frame. That way it stays up out of the way, stays away from the exhaust, and stays away from anything that could rub through the insulation. Pull them all the way back to the bumper, but leave enough wire to work with when you wire the plug (bout 12"). Snip off the leftover from the black wire. While you are doing this step, you can make this as clean as you want. All it is, is time. You could probably fish the wires right into the existing wireloom, or you could run another wire loom right along the factory's, or don't use any at all. It just makes it look a little cleaner, and gives a bit more protection for those wires.

Attach a ring terminal to the black wire you cut off the back, and hook it to the AUX terminal on the 20 amp breaker. String the wire through the firewall where you ran the blue wire. Hook that black wire to the power wire of the controller (usually black). While you are under the dash, attach the white wire you bought to the ground wire on the back of the controller (usually white). String that through the hole in the dash with the other wires. Run that out into the engine bay, and hook it to a good ground somewhere. I usually run to the ground bolt on the core support, unless I can go right to the battery. Battery is the prefered spot to run for ground. Sometimes, if I have to, I run straight down the firewall, and take that ground right to the frame with a 1/4" ring terminal, and a 1/4" screw. It all depends on what is cleanest for me.

The only wire left to hook up on the controller is the stoplight feed wire (usually red). That goes to the cold side of the stoplight switch. There are a number of different places to find that wire, and if I can ever find the book I have at home, I'll post those up. Use any of the splice connectors that you prefer, but a simple scotch lock will work fine.

Tie all of those wires together and tie them up out of the way. Clean up the under side of the dash so that the next time you add something, or if you ever have problems, it will be easier to find the wires you need. A little bit of split loom will go along way here. I've seen some professional installs, that I have to work around, that look like complete trash. I've had to stop and clean up other people's mess more times than I care to count, just to get my stuff installed.

Go to the back of the truck and put in the wiring T-connector. Cut the 4 flat plug off of the end of the T and wire up the 7-way plug at the back. There are a couple of diagrams already here in the towing section, but I will find a good one, or draw one myself, to post here in this thread. There should be the standard color wires on the T. White is ground, brown is running lights, green is right turn, and yellow is left turn. Black is the hot wire, blue is the brake wire, and use the leftovers of the white wire you used for the controller ground for a larger ground on the plug. You may have an extra wire hangin around. You may have a back-up light wire. If you use a 7 way plug, that wire will go to the center pin.

Bring the big white wire out of the plug and attach it to the frame with a 1/4" ring connector and a 1/4" screw.

Now go back up under the hood of the truck and hook up your power. You are probably running out of the black wire, but you only need enough to go from the brass post on the 20 amp breaker to where ever you found best to draw power from. This will put two terminals on the 20 amp brass post, but you want to get power to that post first. That way, the controller is always the first thing to get power. Anything can happen to that wire running between the breakers (gets cut, corrosion, etc...), but the controller will get power... Not having interior lights on your enclosed trailer is way better than not having brakes.

A plug-in brake controller

The factory guys are making things alot easier on us by having most of the wiring run, the power sources found, and all lighting circuits worked out.

Ford has been on the ball for a few years now.

Chevy didn't start until late 99, and that was on late model trucks. When Chevy came out with their "pre-wired" systems, the came out swinging hard, and connected with a home run. Their only fawk up so far, is they moved a wire in the socket for the brake controller. Chevy will have one brake controller harness for 99-02 trucks, and one for 03 trucks. Chevy has also stopped putting the required brake controller harness in the truck when they leave the factory. Ford is currently the only manufacture that still ships their trucks with the harness. Any of you with trucks on order, make sure you get that pigtail before you leave the lot. You paid for a towing package, make sure you get it all.

Dodge... What can I say. Dodge leaves alot to be desired. Dodge is actually the reason everyone started going to a "pre-wired" towing system, but they are still lagging far behind their competition. In the late 80's, early 90's, Dodge was the place to go for the diesel motor. The Cummins was pushing lots of power and everyone was eating it up. The problem was they had a weak headlight switch. Everything ran through the headlight switch. When you got a trailer all hooked up and rollin, there were too many lights. They would burn up headlight switches right and left. A quick fix for this was to wire in a continuous duty solenoid, using the running light circuit for a trigger wire. This solved it, but should you have to? Dodge has finally got their act right for 2003.

Toyota is entering the market and trying their best to get the public interested in thier rigs. They also have a factory plug for a brake controller, and they are also offering 5th whel hitches, and gooseneck hitches, for their full size truck. However, I have yet to see one of these in person. Everyone simply loves diesel trucks around here.

I'm gonna make three seperate posts here to go over the pros and cons of everyones system. I'll steal books from work tomorrow so that I can make a better list of what's going where. For tonight, I'm just gonna list a few short ramblings and general thoughts.


Ford has had a variation on a pre-wired system for a few years now. They started with two wires that no one really knows about. Then they went with the first three wire systems. In the very early 90's they finally started with the four wire plugs. This was to be the basis for what they have today, the 6 wire plug.

Please excuse the quality of this pic. I tried to make it as crisp and as big as I could.

This is where you need to plug it in on Super Duty trucks, 99-03. Turn the 4 quarter turn fasteners on the cover below the steering wheel, and remove the cover.

This is the plug that has been used for the last 7 or 8 years. Depending on the year, it needs to be plugged in in one of two places. On 94-99 F-series trucks (old body style), it is straight down from the radio, at the bottom of the dash. It will be attached to a metal plate, with the plug on the back side. On 97-03 Expeditions and Navigators, it will be down very close to the ALDL connector, at the botom of the dash. Look around in the Explorers and Rangers and you may find one there too.

The four wire systems are fine... They were only used for one or two years, so coming up with a plug could be a chore. I beleive that I saw one in the link I posted in the hardwire instructions. These plugs were used in 92 and 93. That plug is located in the same place as the 94-99 trucks.

To activate the circuits that run the controller and charge wire, you will need to plug in a few relays and fuses, if the previous onwer has not done that already.

The red box is where the relays need to be plugged in. The white box is the Electrical Distribution Center. This is where all of the fuses are. This box sits on the driver's side fedner liner, back towards the firewall.

The number 16 and 28 fuses in this pic need to get 30 amp Maxi fuses. Fuse #16 is the fuse for the trailer hot lead. This will power lights, charge batteries, or whatever you would need a 10 guage 12v+ power wire for. Fuse #28 energizes the wire to power the controller. Also highlighted are the fuses for the trailers lighting systems. Fuse #1 is for the left turn/stop lamp, #3 is for the right turn/stop lamp, and #4 is for the back-up lamps and running lamps. Fuses #1 and #3 are 7.5 Mini's. Fuse #4 is a 20 amp Mini. In 2002, Ford moved these fuses and relays up under the dash.

I have always tried to avoid using Ford's three wire systems. Sure, the wires are there, but I've never been able to find where they are fused, or exactly where they run. I have always ended up cutting the plug off and just using their wires instead of stringing my own, and going with a hardwire type install. You will want to hardwire this controller, and run your own wires.

The two wire systems were so obscure that hardly anyone knows which wires are actually used. Don't worry about even messing with this. Just do a hardwire.


Chevy has got their act together so far. They tested their system in a few trim levels of the Silverado. Specifically in the the late 99 LS and in all of 99 in the LT. Since then, all vehicles will have the recepticle you need, however the trucks without the trailer tow option will only have two usable wires in the plug. The ground wire, and the stoplight wire. The power wire (black) and the brake wire (blue) will terminate right behind the brake booster. Those two wires will have to be run to their respective places. The black wire will need to be run to the battery, through a self-reseting circuit breaker. The blue wire will have to be run back to the plug. In other words, the wires for ground and the stoplight light wire have been found for you, and the rest will be a hardwire install.

This is the plug you will need to connect to the controller.

The receptical can be found in most late model GM trucks. It is placed in what GM calls the "Convenience Center". The old style center is just an open box that is attached to the firewall, about where your left foot is while driving, with a few wires coming out of it, and a few plugs showing.
In 99 (in the trucks listed above) they came out with the new style center. It is located about where your left foot would be while driving. It is an enlosed box that is held shut with a plastic speed nut, and a few clips. The clips are one on each side, and one on top.
Once the cover is removed, you will see rows of recepticals. The one you want to plug into is the second recepticle from the left, on the very top row.

GM also went to seperate circuits for trailer lighting. These fuses are found in the Electrical Center on the driver's side fender liner, under the hood. This box is marked on the underside, so those fuses are hard to miss.


Just like the others, plug in your controller under the dash.

This is the plug you need.

And this is where is gets plugged in at. This great picture was taken by TornadoTJ.

On the new body style trucks (esspecially on the 04 trucks), if you don't see the plug above the big cluster of wires, reach behind there and feel up against the firewall. You won't be able to see the plug, but it may be attached there. That is the blue box.

Something else exciting for Dodge since 03 is the new electrical center on the driver's side fender well, under the hood. Much like Chevy, this is where you will find fuses for all of the seperate trailer wiring circuits.

Just for you guys that need to hard wire a controller on a Dodge truck, I give you This thread where I laid out how to wire a Dodge truck from scratch for Hick. I've already taken the guess work out of it for you. :p

On the 94?-02 trucks (the last body style), you need to watch for something.

Just because the plug is under the dash doesn't mean that the brake wire runs back to the bumper, unfortunatly. You will have to look in two places to be sure that wire is there. Look back under the bumper with all of the other wiring to see if there is a group of wires bundled up and not running to anything. That should be the wires you need. Or, you may have a factory plug attached to the hitch and the wire is already attached to the plug. If those aren't there, but the plug for the controller is, look behind the drivers side fender liner, closest to the cab of the truck. If you are standing looking at the drivers side front wheel, it will be on your right hand side. There should be a couple of wires run to a plug that is stuck to the fender well. Look for one the heavy guage wires that is blue. You should be able to see the wire run into the plug, but not see it come back out. That will be the wire you need to tie into for the brakes. Run a wire, at least 12 guage, back to the brake terminal of the plug, from that blue wire.

Regarding the '03 Dodge:

The plug for the controller is in the upper left of the pedal area. It is light blue. I've marked it here:

As far as placement, I strongly suggest the far right side where the accellerator pedal is. With it too far left the emergency brake pedal will hit it when released, and a little over to the right of that and you'll hit your shin every time you depress the clutch.

As far as the controller, this time I got a Tekonsha Prodigy. It was definitely worth the $125 I paid for it. Best controller I have ever had. I strongly suggest this one over the cheaper models.

They even gave me a pigtail that went directly from the controller to the connector, I didn't have to splice a single wire. It can't get any easier than this!
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And for the Electrical GURU's replace the Connecters with solder. :stan:
And for the Electrical GURU's replace the Connecters with solder. :stan:
when have YOU ever soldered anything in your life? :stan: :stan:
And for the Electrical GURU's replace the Connecters with solder. :stan:
The connections on my Tekonsha Prodigy are all soldered. :thumb:
The connections on my Tekonsha Prodigy are all soldered. :thumb:
Speaking of that, I've got install mine! Truck came with a generic brake controller......piece of crap! non proportional, either on or off, nothing compared to the Prodigy one I bought, but haven't installed fact, I'll go out right now and put that thing on there! I used it twice on my parents Yukon and LOVE the thing!

I have a '94 Chevy, but luckily someone else wired it already!!
when have YOU ever soldered anything in your life? :stan: :stan:
Check out

By far the best controller on the market...but expensive!
I have a Tekonska Prodigy and love it. Without seeing the one above in person, it would be hard for me to believe that anything can work better. And if it is better, I really doubt its 3.5X the performance better, to match the cost increase.
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