Brake Controller Wiring

[floyd]

It is rare to have a "plug and play" for a brake controller on a crossover, even with a factory tow package.
It should be easy to find a ground but the signal wire must be installed downstream of the brake light switch. It is a simple matter of snapping a scotchlock onto the wire. I prefer to use the stacon plug-in type which accepts a blade connector.
Having located the right wire, it should be easy enough to get a friend to make the connection.

[Nor Cal Mike]

Originally Posted by skalywag

I am not sure this helps, but etrailer has a video of their installation:

https://www.etrailer.com/Brake-Contr...eid=2017203458

The video link that skalywag took me to a video on a 2011 Subaru Outback installation that looks pretty close to what I had in mind. It also looks pretty similar to the way that Raz did his. They are picking that brake signal from the rear of the car at the converter box (red wire) and taking it forward to the controller unit. That is pretty close to what my original idea was. Odds are that my 2010 Forester is the same set up. I will take a look. This doesn't look too bad of a project.

[Mike_L]

I installed the (older) units that taped into the rear TV brake line to produce the signal to actuate the trailer brakes. This should only be done by someone familiar with this installation.
Newer units are activated by the electrical signal generated by the TV that also illuminates the brake lights. Many vehicles able to tow trailers have this connection per-wired into the harness. Those that don't should have a location where this circuit can be installed.
In the absence of both you will need to splice into the harness so as to avoid the input from the signal lights, otherwise the trailer brakes may activate when you turn on your signal lights as some vehicles may use the same tail light for both.

[Nor Cal Mike]

After this discussion, I am seriously thinking of going this route. It is the Tekonsha wireless controller. That way all I need to run is the 12v/ battery power back to the 7 pin connector.
https://www.etrailer.com/Brake-Contr...sha/90250.html

I have a couple of months to decide. Thanks all for your inputs.

[brettl]

You definitely can tap the brake light line to get your brake "on" signal for the brake controller. That is exactly what I did. I spliced the brake light wire going to the trailer light controller I installed (your dealer put one on) and ran it from the trunk to the brake controller. It was a much cleaner solution in my case (Volvo) than splicing the switch under the dash.

[Nor Cal Mike]

Just to complete this thread, I decided to go with the Tekonsha 90250 wireless brake controller. The reason; I tame to the conclusion that I didn't feel like messing with the wiring in my Subaru myself and figured that by the time I paid a shop to do it, the controller plus the install would cost just as much or more than the higher priced wireless unit. Another factor is that I am planning to shop around for another slightly heavier rated, tow vehicle in the fall. This unit will easily work with whatever I buy. The only wire I have to run myself is the battery wire to the 7-way plug. No sense in installing a permanent controller in a car that I may not use as a tug more than 2-3 months.

[David B.]

Thank you for the conclusion to the posting.
Dave & Paula

[Nor Cal Mike]

The spring weather is upon us so I gotta get ready to take the trailer out in the great wide world. I ordered the brake controller today from Walmart. They and Amazon have the best price in this model at $235.98. That beat etrailer.com's next lowest price by $60. I went ahead and ordered the 40 amp circuit breaker and 10ga. wire to run the battery charge line from etrailer.com This takes the 12v power to the 7 pin plug the same as with a conventional controller. Our Subaru is already wired with the 5 pin flat connector for the trailer. The 7 pin plug that I already have accepts the 5 pin plug on its back side. Hardwiring the battery charge wire in the tug is the only wire mod needed when using this controller. The brake controller is housed entirely on the trailer rather than the tug except for the brake adjustment knobs that plug into the cigarette lighter inside the tug. It communicates any commands you want to send to the controller wirelessly. I assume it uses some kind of radio signal but am not certain. The controller sources its 12v power from the battery wire at 7 pin connector connector.

[John in Santa Cruz]

Originally Posted by Nor Cal Mike

Just to complete this thread, I decided to go with the Tekonsha 90250 wireless brake controller. The reason; I tame to the conclusion that I didn't feel like messing with the wiring in my Subaru myself and figured that by the time I paid a shop to do it, the controller plus the install would cost just as much or more than the higher priced wireless unit. Another factor is that I am planning to shop around for another slightly heavier rated, tow vehicle in the fall. This unit will easily work with whatever I buy. The only wire I have to run myself is the battery wire to the 7-way plug. No sense in installing a permanent controller in a car that I may not use as a tug more than 2-3 months.

use 10 gauge automotive grade wire for that 12V power to minimize the voltage drop, with a 30A fuse right next to the battery or positive terminal you get the 12V from. You'll want to put a battery isolator on that wire, too, so the RV socket is only powered when the car is running, so the trailer won't run your vehicle battery flat when you're parked.


presumably you'll also need a brake light controller, those are quite simple, and can be wired entirely at the back of the vehicle... typically one wire from each turn signal, a wire from a brake light, and the parking light, and your 12V power, the brake light controller converts that to dual filament left and right, where the brakes and turn signals are the same... these controllers also don't take add load on your vehicle's brake/turn signal circuits so any bulb failure sensor won't trigger, nor will your turn signals go into fast blink mode. something like this, https://www.oreillyauto.com/detail/t.../48845/4379713

[Nor Cal Mike]

In the spirit of keeping the the equipment needed for the trailer in the trailer, I am thinking of installing the battery isolator in the trailer. That would leave only the circuit breaker in the car end. I hope to use the tail light circuit to activate the isolator solenoid. I run with my headlights on all the time while driving. To prevent the battery being run down by forgetting to turn off the lights when parked, Subaru also switches the lighting circuit off at the ignition switch making it impossible to leave the lights on when the key is removed. Does anyone see a problem with using the lighting circuit? Is the lighting circuit heavy enough to activate the isolator solenoid?

[John in Santa Cruz]

you'll still need the light converter onboard... your subaru has seperate parking, brake, and turn signal lamps, a trailer just has brake/turn and parking.

solid state isolators don't need a control signal, they sense the voltage on the tow vehicle side, and if its > 13V, they know the engine is running, and switch the trailer side on to charge the trailer batteries.

if you wire your trailer in a non-conventional way, putting everything onboard the trailer, noone else will be able to tow it.

[gordon2]

Originally Posted by Nor Cal Mike

...Is the lighting circuit heavy enough to activate the isolator solenoid?

Dont know but doubt it would work Is it a CAN bus system? You could try it temporarily and see if the Subi's computer complains.

[RogerDat]

Think it was stated that the running light and turn signal so I would assume brake light is included, all through with the existing flat plug.

You may want to check with the dealer to see if there is an already existing accessory type circuit for trailer battery in the fuse box. A circuit that accepts a fuse of suitable amperage for charging trailer battery and is only energized when engine is running. In some vehicles the "tow package" includes that.

Otherwise I'm thinking the best place for a battery isolator is under the hood and close to the battery. Running a long wire back to run a relay AND provide feed that relay switches makes little sense. Solid state isolators that detect voltage may get a somewhat low reading with a long run of wire and with plug connections thus not charging.

It would be sort of a mis-match to the standard 7 pin plug since those will almost always have the isolator already in place under the hood and before the line runs to the 7 pin plug. Or conversely if you tow anything else with a 7 pin your tow vehicle batter can be flattened by any other trailer that will almost certainly not have an isolator.

[John in Santa Cruz]

oh, I missed that there's already a 'flat 4' plug, yes, that means there's already a trailer light converter, so all I said about that can be ignored.

I concur, the trailer isolator belongs under the hood, near the battery (or positive terminal, if the subie has one handy)...
something like this: https://www.amazon.com/Smart-Battery.../dp/B00400IYTK

wired like...
power(+) -- fuse -- isolator --------- RV plug.

that isolator also needs a ground wire. note there are different types of isolators, the one I linked is voltage driven, rather than controlled by a separate wire connected to the ignition. I would use like a 50A fuse, I think, because if the trailer battery is seriously drained when you start the engine, there can be quite a lot of initial current.

[Nor Cal Mike]

The Tekonsha Prodigy brake controller arrived today.



The brake controller mounts on the tongue of the trailer. It has it's own chord with 7 pin plug on the front end that is connected into the 7 pin plug on the tug. It also has a 7 pin receptical on the opposite (rear) end. The original 7pin plug on the trailer plugs into the module there.



The control knobs and digital readout that gives the driver the dial up/ dial down brake adjustment in the cab are located in a box which has a chord extending from it to a standard 12v. plug plug-in to source power from the dashboard cigarette lighter. It communicates with the controller module mounted back on the trailer wirelessly.