how to wire a brake controller

[tcp]

I have a bit of electronic prototyping experience and here's my layout.

From the battery I have a 6gauge wire running through a 50 amp maxifuse at the battery, then across the engine bay to a project box. inside the box the 6guage branches off to three automotive relays rated at 30/40 amps each. Each also has another glass fuse holder and appropriate fuse for their function. These relays turn on with the ignition but can be disabled with secondary switch on the box so I can kill their function when not towing.

The first relay transmits power through 2 12guage wires right through the firewall, the door sill panels on the passenger side and back to the 7way connector whose wires run through a grommet in the folding seat bin. Those are to charge the trailer batteries while driving.

The second relay runs inside and to the brake controller cannon plug to power the controller. The cannon plug is there to take the controller out when not using it. There are wires from there to the brake switch and also back to the 7way plug along the same route as the charging wires.

The third relay sends power back the a second project box that is one of the rear armrest cubbies for the third row seats. There are also wires running to there from a 4pin wiring harness that i originally installed. It had plugs that took the current from each rear signal lamp to run the trailer signals/brake lights and running lights. Inside the second project box are 3 more 10 amp relays that take the signal from each turn/brake output from the original harness and use them to turn on the relays which are powered from the larger power wire from the front. That way I don't "load" my vehicle lighting to run the trailer lights/signals/brakes. they just trigger the relays at a couple of hundred milliamps and the main power for everything comes right from the battery.

More than I probably needed to do, but it was a project I enjoyed.

[brian_bp]

Nicely done, tcp! That sounds very tidy and thoroughly thought out.

I ran the battery charging and controller output wires to the rear under the floor, primarily because I am more comfortable with working on the ground under a vehicle than digging through interior panels - both approaches can be good options.

Brake controller manufacturers normally advise supplying power from the battery with only a circuit breaker, and no other switches, no relays, and no fuses.

• I like the master cutoff switch idea (I did this too, but only on my battery-charging line), but I did not want a switch in my controller supply in case I ever hooked up and pulled away without turning it on. Of course the controller would show the lack of power, but if I'm too rushed to flip the switch...
• Relays are pretty reliable, but if the one in the brake controller circuit fails, there will be no trailer brakes.
• Fuses are good to protect circuits, but the usual recommendation is for an auto-reset circuit breaker (ARB) instead. The fuse should never blow, and if it does due to an electrical fault then there's no way around at least a temporary loss of braking power, but if it just fails due to the high-vibration environment of a vehicle then there's no way to get the brakes back until stopping, and no obvious warning that the brakes are non-functional. An ARB resets itself if tripped, so it recovers from a momentary overload.

[brian_bp]

I've looked into the T-one wiring harness on etrailer.com
However, this converter has a very weak electrical specification of 4.2A for the tail lights.
I figure that the two tail lights plus 11 small rear and side lights on my pop-up trailer require 4.8A (at 14V).
So, a bit stronger converter is needed.

I looked at my trailer and found it had the 11 lights too, so...

What about removing the bulbs out of the three middle running lights on the rear of the trailer to reduce amperage load?
...

Eleven running lights is the usual consequence of needing wide-vehicle identification and clearance lights

• two clearance lights facing forward showing the height and width
• two side markers on each side
• two clearance lights facing rearward showing the height and width
• a cluster of three in the middle of the rear to indicate that the trailer is over 80" wide (the identification lamps)

If the tail lamps are used as the rear clearance lights (only for low enough trailers), that's eleven; if the clearance lamps are on top and the tail lamps are separate, that's 13 lights operating.

The only problem I see with disabling that group of three in the rear (if it is identication group that Rod is suggesting to pull) is that these are legally required for vehicles over 80" wide... and most travel trailers (including mine) are at least that wide. Most of the moulded fiberglass travel trailers (such as the original size of Boler and Trillium) were just barely 80" wide, and I think that was done to avoid the requirement for the extra lighting.

[tcp]

You're right on all counts. I actually do have a breaker available and probably should have gone that route, but i'm OK with my layout. The fuse ratings are quite high for a single axle trailer that draws 3 amps for each brake. I have the fuses set at 30amps to deal with a direct short on the brake lines. If I have a direct short on a line with a breaker, it's going to set/reset itself continuously anyway and the pulsing action of having brakes turn on/off may be more detrimental in an emergency situation. I figure i'll burn away the Sienna's brakes if there is a failure at the trailer end and I'll have to replace a lot of stuff.

Nicely done, tcp! That sounds very tidy and thoroughly thought out.

I ran the battery charging and controller output wires to the rear under the floor, primarily because I am more comfortable with working on the ground under a vehicle than digging through interior panels - both approaches can be good options.

Brake controller manufacturers normally advise supplying power from the battery with only a circuit breaker, and no other switches, no relays, and no fuses.

• I like the master cutoff switch idea (I did this too, but only on my battery-charging line), but I did not want a switch in my controller supply in case I ever hooked up and pulled away without turning it on. Of course the controller would show the lack of power, but if I'm too rushed to flip the switch...
• Relays are pretty reliable, but if the one in the brake controller circuit fails, there will be no trailer brakes.
• Fuses are good to protect circuits, but the usual recommendation is for an auto-reset circuit breaker (ARB) instead. The fuse should never blow, and if it does due to an electrical fault then there's no way around at least a temporary loss of braking power, but if it just fails due to the high-vibration environment of a vehicle then there's no way to get the brakes back until stopping, and no obvious warning that the brakes are non-functional. An ARB resets itself if tripped, so it recovers from a momentary overload.

[jh818]

I never found a plug for the brake controller. I have it all installed, except for the wiring harness for the controller itself. Since I am installing in two vehicles, I need to order a second controller for the Sienna, wire it to the brake pedal, and plug in the power from the battery and brake power (which are both already installed and ready to go).

I guess the Sienna was not pre-wired for a brake controller.

I am thinking about getting a brake controller and using it for both my 07 Sienna LE and 01 4Runner SR5. I was wondering if i could get an additional wiring harness to wire up the other vehicle so I can use the same brake controller? I doubt the 4Runner is pre-wired either. Any suggestions?

[tcp]

I can use my controller on either of my vehicles. I have all the wiring brought up to a quality 4 pin connector in each vehicle, something along this product line:

http://www.ittcannon.com/product.aspx?id=1102

Then I put the mate for it on the wiring from the controller and it mounts up in each vehicle with a twist of the connector.

I never found a plug for the brake controller. I have it all installed, except for the wiring harness for the controller itself. Since I am installing in two vehicles, I need to order a second controller for the Sienna, wire it to the brake pedal, and plug in the power from the battery and brake power (which are both already installed and ready to go).

I guess the Sienna was not pre-wired for a brake controller.

I am thinking about getting a brake controller and using it for both my 07 Sienna LE and 01 4Runner SR5. I was wondering if i could get an additional wiring harness to wire up the other vehicle so I can use the same brake controller? I doubt the 4Runner is pre-wired either. Any suggestions?

[brian_bp]

I guess the Sienna was not pre-wired for a brake controller.

Unfortunate but true... this is what I was referring to in my earlier comment.

I doubt the 4Runner is pre-wired either.

I would guess that the 4Runner is pre-wired, if only because it shares the same platform as the Tacoma pickup.

I am thinking about getting a brake controller and using it for both my 07 Sienna LE and 01 4Runner SR5. I was wondering if i could get an additional wiring harness to wire up the other vehicle so I can use the same brake controller?

If the controller has a connector on it so that it is normally a plug-in installation, it is supplied with a harness of that connector and a set of wires; this is the case for the popular Prodigy and some others, and additional harnesses are available from the controller manufacturer. For the 4Runner, it may be possible (depending on the controller) to buy a harness which is already set up to be simple plug-in to the vehicle's prewired setup: in that case, the generic harness which comes with the controller could be installed in the Sienna and left there, while the vehicle-specific harness is used in the 4Runner. The manufacturers of some controllers promote this portability as a feature of their plug-in designs, but tcp's custom solution works for any controller, and any number of vehicles, even if the controller was not designed as a plug-in.

[jh818]

I doubt the 4Runner is pre-wired either.

I would guess that the 4Runner is pre-wired, if only because it shares the same platform as the Tacoma pickup.

Thanks, brian_bp. I will need to double check. It already comes with the 4 pin and hitch receiver from the dealer when we bought it new. I hope there is the wiring already so all i would need to get is the 7 pin pigtail.

[RonF]

brian bp,
I had the same problem of 11 lights and the current draw. I replaced all of the bulbs with LEDs. They draw about 1/10th of the incandescent bulbs.
RonF

[brian_bp]

brian bp,
I had the same problem of 11 lights and the current draw. I replaced all of the bulbs with LEDs. They draw about 1/10th of the incandescent bulbs.
RonF

I agree - that's the solution. I just haven't done it yet on our trailer, and since we are not currently using that trailer I may never get to it. The LED swap also only solves the problem for that specific trailer.

[DaveR]

I just installed a receiver, 7-pin wiring, and a Prodigy P2 brake controller on my 2006 CE. This board was a great resource, and I appreciate everyone who has posted helpful information.

I bought the "standard" parts from eTrailer.com, which was another great source of information. Everything was technically easy and straight-forward. The biggest difficulty for me was installing the receiver onto the frame, because the bolt holes were so corroded. Anyway, I saw a few different posts here that asked about wire routing through the firewall. I took a few photos which may be helpful.

1. This photo is supposed to show the general location of the rubber grommet that I used. You can't actually see it in the photo because it's so far under the wipers, but it's easy to find if you follow the bundle of wires I marked with the red arrow. You can also follow the hood release. Note that removing the top of the air filter box will give you a lot more room to work.





2. This photo is a bit fuzzy, but it shows the grommet itself. I put a red circle around the nipple that I used.





3. Here's a clearer picture of the grommet, with two wires sticking through. I had a total of three wires that I had to run through the firewall, and I used the same nipple for all three. I ended up removing the wires shown in the photo, and ran a single wire through from the engine compartment. Then I went back and ran these wires through from the footwell. I don't think I could have easily ran the single wire through, from the engine compartment, with these two wires in place. I had some dielectric grease handy, so I put a dab on the end of the wires, which made it easier to feed them through. Anyway, this all wasn't nearly as frustrating as I thought it would be, despite the difficult location.




4. Here's a photo of the grommet from the footwell. It's located up under the dash, to the left (as you face the front of the van) of the steering wheel. The nipple that I used is circled, and I had to snip the end off before I could feed the wires through.





5. This last photo just shows where I mounted the brake controller. I couldn't find what I would consider a great location for it...but this should work well for me. I can see it well, and I can easily reach it. This location could be a problem for someone who sits very close to the dash, but my wife and I both drive with the seat all the way back and there is plenty of room for knees. If you mount the controller as shown, you have to make sure that it (the controller AND the wires) isn't in the way of the hood release.





Again, thanks everyone for all the helpful info. I hope these will make it easier for someone else.

[brian_bp]

Thanks for the description and illustration, Dave.

5. This last photo just shows where I mounted the brake controller. I couldn't find what I would consider a great location for it...but this should work well for me. I can see it well, and I can easily reach it. This location could be a problem for someone who sits very close to the dash, but my wife and I both drive with the seat all the way back and there is plenty of room for knees. If you mount the controller as shown, you have to make sure that it (the controller AND the wires) isn't in the way of the hood release.

There was a collection of illustrated brake controller mounting locations in the old SiennaClub.org forum, and we tried to create something similar in Where did you mount your brake controller?, but we don't have much there... Dave, could you add your mounting photo and description to that topic? You might find my solution (illustrated there), or the common in-the-bin location, interesting.

Many years ago vehicles had fewer features so there wasn't much on the dash, and the dash was a simple flat panel... that made it easy to slap in a controller. Now there are switches and displays for a myriad of features so there are few blank spots, and the interior is a complex shape with the dash wrapping around the driver in what everyone who has never been at the controls of a plane calls a "cockpit" effect... leaving nowhere for a tacked-on component. Heavy-duty pickup trucks have factory-available controllers designed into the dash, but it's a challenge for the rest of us.