Brake Controllers on cars that might brake automatically

[boley]

Hello all,

I am currently in the market to add a fiberglass camper to my adventure assault fleet. However I am currently stumped by one thing: Is it safe/plausible to hook up a brake controller on a car that has automatic safety features that may apply brakes?

My specific case is a 2013 Subaru Outback with Eyesight. The Eyesight system basically consists of a few cameras that monitors the road and other vehicles movement relative to my car. In an unsafe situation it can apply braking to keep me from rear ending someone. Many cars do similar things - heck the Volvo salesman was determined that I try to ram a barrier with their system armed.

The problem is that I have no idea if the Subaru system (or any of them) send a proper signal to the brake switch. For all I know these system bypass the brake switch and trigger the brake lights through some other wiring scheme. The big obvious concern is that if the brake switch is not energized, the brake controller splice connector will not be energized, and therefore the brake controller will not fire off. Worst case scenario is an aggressively braking car and no trailer brake activation. Bad juju.

Does anyone have any experience with similar systems or a solution? Or am I just worrying too much.

Thanks

[floyd]

Originally Posted by boley

Hello all,

I am currently in the market to add a fiberglass camper to my adventure assault fleet. However I am currently stumped by one thing: Is it safe/plausible to hook up a brake controller on a car that has automatic safety features that may apply brakes?

My specific case is a 2013 Subaru Outback with Eyesight. The Eyesight system basically consists of a few cameras that monitors the road and other vehicles movement relative to my car. In an unsafe situation it can apply braking to keep me from rear ending someone. Many cars do similar things - heck the Volvo salesman was determined that I try to ram a barrier with their system armed.

The problem is that I have no idea if the Subaru system (or any of them) send a proper signal to the brake switch. For all I know these system bypass the brake switch and trigger the brake lights through some other wiring scheme. The big obvious concern is that if the brake switch is not energized, the brake controller splice connector will not be energized, and therefore the brake controller will not fire off. Worst case scenario is an aggressively braking car and no trailer brake activation. Bad juju.

Does anyone have any experience with similar systems or a solution? Or am I just worrying too much.

Thanks

Eventually , even Rube Goldberg himself would be overwhelmed!

[Andrew Gibbens]

You mean they might fit a 'safety system' that braked the car but did not illuminate the brake lights (and hence triggering the brake controller)? Not much chance of that.

[boley]

Originally Posted by Andrew Gibbens

You mean they might fit a 'safety system' that braked the car but did not illuminate the brake lights (and hence triggering the brake controller)? Not much chance of that.

Not saying that at all. I am simply saying it may not trigger the Brake Switch and just light up the brake lights via another circuit. The brake lights absolutely activate when the emergency braking kicks in.

Based upon what I can figure out, the Brake Switch circuit is what triggers a brake controller to activate, not just brake light action. I have reached out to Subaru for clarification on the wiring, but have not heard back. My hope was that another owner here might have more experience with such systems.

[Roy in TO]

Andrew,
If I understand boley correctly. Historically controllers are activated by the brake light switch at the pedal. The new automatic systems activate the brakes and brake lights without the brake pedal depressed. So where does one connect the controller such that the trailer brakes come on with both manual and automatic braking?

Perhaps this is a question for the companies that make the controllers such as Tekonsha since the number of vehicles having such systems will only increase in the future.

[Jon Vermilye]

It could be a problem. My RAV4 has the ability to slow down the vehicle with the cruise controller. If you hold it in the "slow down" position long enough it puts the brakes on. The manual states is does not turn on the brake lights under those conditions. As far as I can tell it doesn't put the trailer brakes on either, although I haven't used the feature enough to be sure.

[Eddie Longest]

I agree with Roy, Tekonsha should have the answer. I just installed a controller on an Outback which has four wires going to the brake switch. They had schametics to determine which wire I needed to connect the controller brake wire to.
Eddie

[Raz]

When I wired my Forester, Subaru provided a connector for trailer lights back under the cargo area cover. I bought a light converter from etrailer that plugged in to it and generated the 4 pin light connection. One of the wires (red I think) into the converter is the brake lights. I spliced in there for my brake controller input. It avoided messing around with the very hard to get to brake pedal switch. Raz

[Thomas G.]

Could you wire the brake controller such that it is triggered off the brake light circuit itself, as opposed to the brake pedal switch? That might entail a wire forward from the tail light area.

[Brian B-P]

Vehicle manufacturers have arranged automated systems to power the brake light control circuit at the factory-provided connection to the trailer brake controller. It seems less likely that they would ensure that the circuit was powered during automatic braking if they were not making any specific provision for towing.

Either way, I would want to check to be sure. In this case, a run at a harmless (cardboard?) barrier might serve to trigger the system, and a simple test light can watch the circuit of interest.

In any case, I don't think I would be too concerned about it, because I would expect my foot to be planted on the brake pedal within a second of the automated braking action. I also fundamentally dislike the idea of automated brake application...

[Brian B-P]

Originally Posted by Thomas G.

Could you wire the brake controller such that it is triggered off the brake light circuit itself, as opposed to the brake pedal switch? That might entail a wire forward from the tail light area.

I agree that's a potential solution if there is a problem with the automated system; however, if the brake controller puts too much load on the circuit, it could confuse a tail light monitoring system. No vehicle I have owned has monitored its lights this way, but they also don't apply their own brakes.

[Roy in TO]

Originally Posted by Brian B-P

I also fundamentally dislike the idea of automated brake application...

But we must remain cognizant that some of the AWD systems use selective timed braking to a spinning wheel such that even torque is applied to the remaining wheels with traction. The 4matic flashes a bright orange triangle when this happens.

This is done without brake lights. The requirements of feeding an appropriate signal to a brake controller are becoming more complex.

[Brian B-P]

Originally Posted by Roy in TO

But we must remain cognizant that some of the AWD systems use selective timed braking to a spinning wheel such that even torque is applied to the remaining wheels with traction. The 4matic flashes a bright orange triangle when this happens.

This is done without brake lights.

Yes, but the vehicle doesn't slow down: that's why the brake lights are not applied, and why trailer brakes should not apply in this case (so it's good that the controller doesn't get a brake light signal). This isn't just an AWD feature; it is normal for any traction control system - even my decade-old 2WD Focus does this. Because it is just adjusting power delivery, not decelerating the vehicle, I'm fine with it.

Originally Posted by Roy in TO

The requirements of feeding an appropriate signal to a brake controller are becoming more complex.

I agree. The sensible thing to do now is to integrate the trailer lighting and trailer brake control with the vehicle's networked communications. This will take more work than North American towing equipment manufacturers seem willing to invest... perhaps because as consumers we are generally not willing to pay. Euro suppliers do integrate with tow vehicle systems for lighting; however, they don't use electric brakes so their products don't offer an option for brake control integration.

[boley]

I really appreciate the feedback in this thread. At this point I have still not heard back from anyone at Subaru North America in regards to the specifics of the Eyesight system. Right now I suppose there are 2 viable options to combat cars that may automatically brake:

1) Use surge brakes.

2) Disable the auto-braking safety feature in the tow vehicle. This is probably the route I will take until something more robust appears.

[mcbrew]

Originally Posted by P. Raz

When I wired my Forester, Subaru provided a connector for trailer lights back under the cargo area cover. I bought a light converter from etrailer that plugged in to it and generated the 4 pin light connection. One of the wires (red I think) into the converter is the brake lights. I spliced in there for my brake controller input. It avoided messing around with the very hard to get to brake pedal switch. Raz

I'm curious... With this setup, do your Forester's tail lights illuminate when you use the manual lever on the brake controller?

[Carol H]

I would do neither

As others have suggested if it a Tekonsha Prodigy controller Tekonsha should be able to provide the actual instructions for your Outback. Lots of vehicles these days have the same auto braking safety feature. When I had mine installed on my Outback the people who installed it got the instructions from Tekonsha for the hard wiring and they only called the Subaru dealer to get an idea on the best/easiest spot that Subaru recommended for putting the wiring through the firewall.

You might even find your answer on a Subaru discussion form.

[Raz]

The brake light input on the brake controller is a high impedance input, that is it will not load what it is connected to. If it draws microamps I would be surpassed. As such you can connect it to any point where the brake light voltage is present and remains constant for the duration of the pedal activation. Anything that's pulsed could be an issue.

Originally Posted by mcbrew

I'm curious... With this setup, do your Forester's tail lights illuminate when you use the manual lever on the brake controller?

Since the brake controller, when activated, supplies power only to the brake magnets on the trailer, activating the manual lever should not effect the lights. (Creative wiring excepted. ) Raz

[Carol H]

Originally Posted by mcbrew

I'm curious... With this setup, do your Forester's tail lights illuminate when you use the manual lever on the brake controller?

As Raz indicated using the manual lever on the brake controller should never impact the brakes or lights on the car.... the whole reason for using the manual lever is to apply brakes to trailer only in order to help control a sway situation more effectively.

[Roy in TO]

I like to consider the trailer brakes as my back up emergency brake system. My current 94 Ranger has had more brake failures than all of my other vehicles combined. I can safely say that I can add all of Carol Ann's vehicles into that mix. We regularily service our vehicles.

[Brian B-P]

Originally Posted by P. Raz

Since the brake controller, when activated, supplies power only to the brake magnets on the trailer, activating the manual lever should not effect the lights.

I do not believe that this is true for a typical controller.

Originally Posted by Carol H

As Raz indicated using the manual lever on the brake controller should never impact the brakes or lights on the car.... the whole reason for using the manual lever is to apply brakes to trailer only in order to help control a sway situation more effectively.

I agree that manual activation of the trailer brake controller should not affect the tow vehicle's brakes, but it can run the lights of both the trailer and tow vehicle. The controller can put out power on the brake light switch wire (which is normally used only as an input). For examples...

The manual for the Curt Discovery controller lists "Manual Control activates brake lights" as a feature, and in the Manual Control section:

The Manual Control activates the tow vehicle and trailer stoplights.

Draw-Tite Activator 5100 manual:

The manual control activates the tow vehicle and trailer stoplights and the output indicator on the control unit.

Hayes Energize operation manual:

• The tow vehicle and trailer brake stoplights will be illuminated during the manual lever activation

Dexter Predator DX2 instruction sheet

The tow vehicle and trailer brake stoplights will be illuminated during the manual lever activation.

The wiring of this controller calls for a 20 amp fuse on the red brake light wire; for a signal to the controller one amp would be lots, so the 20 A is to handle the power to run the tow vehicle and trailer lights.

In the Valley Journey HD installation instructions among the Features:

Stop Lamp Activation - When applying the trailer brakes by utilizing the manual slider alone, the Journey HD will supply power to the trailer’s brake lights.

When installed in the usual manner, the controller's output on the brake light switch wire should be seen by the tow vehicle's stop lamp circuit exactly like the brake pedal being pressed, so both the tow vehicle and trailer brake lights should come on. When installed as Raz has done, the result will depend on the wiring in the tow vehicle for trailer lights: if they are simply tapped in, the controller will light up both vehicles; if there is an isolation circuit, the tow vehicle's lights may not operate but the trailer should.

I don't know if all trailer brake controllers include this feature, but a vehicle braking without stop lamps illuminated is generally bad, so I would expect the best practice to be to include this feature. Many of us use Tekonsha controllers, such as the Prodigy series, and I don't see any reference to running lights during manual activation in their installation manuals or FAQs; however, I also don't see a warning that lights will not be illuminated.