Trailer breakaway system

1DRR406 · August 12

Saw this in a recent post.

"Reminder, your breakaway brakes will not work with the battery switch off. Always leave the switch on while towing."

I believe this to be incorrect. My understanding is if you were to brake that connection ( or activate the breakaway system by pulling the pin while parked) you will have a battery drain, regardless, of the battery disconnect switch is on or off.

Need a straight answer. As I have been towing with the battery disconnect, switch off.

What does the wisdom of this forum say?

Thank you all.

swiftwave · August 12

My understanding is that this may vary in different trailers, depending on how they are wired. It may even vary in trailers from the same manufacturer in different production years.

It is possible to wire a trailer so that power from the battery bypasses the battery disconnect switch and flows directly to the breakaway brakes.

It’s also possible to route the power through the battery disconnect switch, thus allowing the disabling of the breakaway brakes by turning off the battery disconnect switch.

To test a trailer, a person could jack a wheel off the ground and see if it spins when the breakaway pin is pulled and the battery disconnect switch is off. (Of course, the 7-pin connector must be disconnected during this test.)

AnOldUR · August 12

Here's a wire diagram I found for a 2019 320S. It shows that the breakaway brakes need the battery switch on to get power to the brakes when not connected to the tow vehicle.

I've always thought that my 2020 320S was the same. Has nuCamp changed this on newer or different models?

Image: https://us.v-cdn.net/5021717/uploads/editor/u4/dxi4mudw2ngm.jpg

qhumberd · August 12

It is clear from the wiring diagrams that have been discussed on this forum that the 400 is wired so that the power to the trailer brakes is received from the trailer battery in event of a TV disconnect. This circuit is NOT powered with the battery disconnect off. I believe this should be easy to confirm on a trailer as follows:

1. You can jack up one wheel with the trailer 7 pin disconnected from the TV. Trailer battery is ON (battery disconnect in ON position).

2. Pull the emergency breakaway pin on the frame and the lifted wheel should lock up with brakes activated.

3. Then turn the battery disconnect to the OFF position (trailer battery is OFF) and the power to the trailer brakes should cease and release the brakes, allowing the wheel to turn again.

Allowing a critical safety component to be disconnected by the owner due to the confusion you described is clearly not optimal. You would hope that a design is possible that would remove the human factor.

If the above procedure is incorrect I would really like to hear about it.

Thanks

PS: The circuit below does not include the breakaway switch, but shows the disconnect in line with the terminal going to the brakes

Image: https://us.v-cdn.net/5021717/uploads/editor/ro/bzhunxpyoade.jpg

MuttonChops · August 12

Based on reports if Owners, trailer wiring for all nüCamp trailers with a factory installed battery cut-off switch require the Cut-Off Switch to be "On" for Emergency break-away brake operation. The wiring is as shown in @AnOldUR 's post above.

As @swiftwave noted other manufacturers may use different approaches. For example: InTech (Sol) trailers have an extra small rechargeable battery built into the break-away system so their trailers do not use/require the 'house' battery to be "on" {the extra battery needs to be tested on a defined schedule}.

nüCamp Trailers do require the house battery to be On:

Sharon_is_SAM · August 12

This from the nuCamp knowledge base - see highlighted text at the bottom.

How to Hitch and Unhitch Your Trailer

Hitching and unhitching your trailer might seem intimidating at first, but with a few simple steps, you'll be ready to tow with confidence. Whether you're a first-time owner or just need a refresher, this guide will walk you through the process and help ensure you're hitting the road safely.

Hitching Your Trailer

Follow these steps to securely hitch your trailer to your tow vehicle:

1. Align Your Vehicle and Trailer

Make sure your trailer and tow vehicle are lined up in a straight line. This helps the hitching process go more smoothly.

2. Adjust the Trailer Height

Raise or lower the trailer coupler using the jack so it clears the ball hitch on your tow vehicle.

3. Position the Coupler Over the Ball

Carefully move the trailer forward so the coupler is directly above the ball.
If you're working alone, you may need to back the vehicle up so the ball is directly underneath the coupler.

4. Lower the Coupler

Ensure your vehicle is in park with the emergency brake engaged. Use the jack to lower the coupler onto the ball until it is fully seated.

5. Secure the Coupler

Engage the latch to lock the coupler in place.
Remove the safety pin from the trailer jack wheel and insert it into the coupler latch for added security.
Store the jack wheel in the front tub.

6. Attach the Safety Chains

Cross the chains underneath the coupler before attaching them to the tow vehicle.
Crisscrossing provides a cradle in case the trailer becomes disconnected.
The chains should not be twisted. If they’re too long, use a quick link to adjust the length. These can be found at automotive stores or online.

7. Connect the Emergency Breakaway Cable

Secure the breakaway cable to the tow vehicle using a carabiner or clip.
Do not loop the cable through the safety chains. In the event of a disconnect, this cable activates the trailer's electric brakes.

8. Plug in the Seven-Way Connector

Connect the seven-way pin from the trailer to your tow vehicle.
Test your brake lights, turn signals, and running lights to ensure everything is working correctly.

Additional Tips:

Make sure your trailer is as level as possible. If not, you may need a rise or drop receiver.
Check that your battery disconnect switch is in the green/on position so the emergency brakes have power.

Once everything is secured and functioning properly, you're ready to hit the road!

Yoshi_TAB · August 12

“Allowing a critical safety component to be disconnected by the owner due to the confusion you described is clearly not optimal. You would hope that a design is possible that would remove the human factor.”

Hi, Can not agree more, I find it totally unacceptable that is the case. When I had my 320, I wired it independent of the switch. It’s such an easy fix. In the world of safety hazard analysis , this would be an unacceptable risk requiring a fix.

I thought they may have addressed this in the 360 as there is no mention in the manual of needing to have the switch on for the safety critical device. I emailed Nucamp to see if anything had changed in the 360 which it hasn’t. They were surprised it wasn’t mentioned in the manual.

Bayliss · August 12

@1DRR406, this discussion tends to come up from time to time. Here is a previous discussion on the same topic that may be of interest, but the conclusions and diagrams are the same/similar to those provided in response to your question:

https://tab-rv.vanillacommunity.com/discussion/comment/128424#Comment_128424

This link includes my wiring diagrams that show the path of both the trailer breakaway power and charge line:

https://tab-rv.vanillacommunity.com/discussion/comment/215901#Comment_215901

I have tested my 2019 320 S Boondock Lite to confirm that the battery disconnect switch must be "on" for power to be supplied from the trailer in the event it becomes unexpectedly disconnected from the tow vehicle (e.g., in a collision.) It is possible to wire it so that you always have power (with or without the switch "on"), but I see no value in doing that.

In my case, I prefer to always have power (from the trailer battery) available inside my trailer, including while towing, such as when I stop for a snack or some other reason, especially at night when I need light available inside the trailer. My 2025 Toyota Tundra includes an isolation relay, so when the tow vehicle ignition is "off," but the 7-way cable remains connected, my trailer is not pulling 12V power from my tow vehicle. This isolation relay is helpful, because I do not need to disconnect my 7-way cable when I stop somewhere for the night.

Also, if you are charging your trailer battery via the 12V charge line (included within the 7-way cable from your tow vehicle) while towing, you will want power to be able to make its way to the trailer battery (uninhibited by the battery disconnect switch cutting off that power.) Of course, if you prefer, you can install a separate charge wire (e.g., with a DC-to-DC charger) that eliminates that concern.

Bayliss · August 12

@elbolillo, I have no reason to doubt what you are saying, so thank you for the clarification. I suppose I should have said that I assume it has an isolation relay, but I have not visually located a relay in the engine compartment, so maybe there isn't one present. However, I just did a quick Google search and the "AI" result (for whatever that's worth) said that the 2025 Tundra does have an isolation relay, particularly the models that include the 7-way power cable. I will do some more research on that. If your Sienna is a hybrid, it appears (again, just a quick search result) that it may be wired differently, using a battery management system.

I did not use a multimeter to test the 7-way outlet on the Tundra with the ignition "on," and then "off." Instead, I was simply testing for power using the lights in the trailer to confirm power available from the charge line while the truck ignition was "on," but no power when the ignition was "off."

elbolillo · August 12

MuttonChops · August 12

This is starting to get ' off topic ' with the tow vehicle isolation relay ' remarks . . .

My 2¢

on that - - - rant?

Inclusion of trailer 7-pin +12VDC isolation when the TV engine is not running varies widely by TV year-make-model and should be checked by every rig owner to confirm their actual wiring situation.

Unfortunately USA Manufacturers have tended to eliminate Trailer +12VDC Isolation Relays from their products in the past years. An example; for years & years a GM Built TV with the factory 'tow package' would have the relay . . . while my 2017 GM product does not. If fact it does not even have an empty relay position on the main fuse/relay panel. Part of the Big-3 overall programs to 1) reduce weight {yes only a few ounces} and 2) reduce build cost {increase greed profit margin}.

On the 2017 I installed my own isolation relay - - but when one considers the truck has many 'for towing' features like tow/haul transmission mode, suspension rake to reduce rear sag, increased radiator size, an additional transmission cooler, and the factory tow package . . . one would think the Isolation Relay would be included or at least just a simple aftermarket plug-in-it . . .

We live in a consumer driven economy with huge corporations focused on the lowest production cost, lowest feature set product the majority of buyers will accept . . . so we buy what is available and modify or live with the corporate profit driven 'close but no cigar' product offering . . .

1DRR406 · August 12

Got the answer, is not exactly sure, by the way question would be related to a 2022 400, I will follow this advice given above

"Check that your battery disconnect switch is in the green/on position so the emergency brakes have power."

Until I perform a simple hitch up, no 7 pin connection, give a pull, switch on, switch off, w/ brake away pin pulled. Easier than a jackup..

Thanks for the words, although? Straying from the subject matter, here is kind of annoying. Am I to be sorry I asked. I should have done a topic search.

DIDO

"THIS IS get ' n 'off topic ' with the tow vehicle isolation relay ' remarks . . . "

Mickerly · August 13

The '320 owners manual from 2019 and earlier, on page 16, says the emergency brakes are powered with the battery disconnect open (OFF). This is incorrect. If it was correct, there would be a second battery to power the emergency brakes. I confirmed the need to have the disconnect closed (ON) by spinning the tire as described earlier.

In the 2020 and newer owner's manual corrected the error. The battery must be ON when towing. Because my CS has an electric refrigerator, we always towed with the battery on so the car could power the trailer.

pthomas745 · August 13

When this has come up before, there were always a couple of owners with the trailers with build dates just around the time where NuCamp started installing battery disconnect switches, who would tell me their emergency break away brakes worked no matter which way the disconnect switch was positioned. They were Unicorn trailers, most likely.

The easiest way to test in a newer trailer with a Victron device: with the battery switch on, pull the emergency brake pin, and have a look at your Victron. It will show a constant 6 amp draw while that pin is pulled out. Turn the battery switch off and have a look at the Victron again and note the 6 amp draw should disappear.

For those of you who have not "pulled the pin" on the emergency break away switch: it is very hard to pull out. It is even much harder to get back in. The pin is small, and not conducive to being "pushed" back into the breakaway "box" there on the tongue. My wimpy hands could not get enough grip to shove it back into place. I used a pair of pliers for a good grip and better force.

ScottG · August 13

This has been a hot topic--and a bone of contention--since I joined the forum in 2015. It's a discussion I have waded into many times. I'll echo everything that has been said previously, and add that I have never heard a credible report of a factory-configured T@B whose breakaway brakes worked if the battery switch was off and the trailer was separated from the tow vehicle's power supply.

When I installed my own battery cutoff in my 2015 (they weren't standard equipment then) I placed it inside the cabin between the 7-pin junction box and the power center. This allows the breakaway brakes to work--and allows the tow vehicle to charge the battery while in transit--regardless of the switch position. I know of at least a couple other owners who did something similar, but to the best of my knowledge the factory approach has always been to install the cutoff at the battery positive terminal. This cuts power between the battery and the junction box, effectively isolating the battery from everything else in the trailer except the solar panels (which in most cases appear to be wired directly to the battery).

I agree--and have argued many times--that this is not an ideal design. And it hasn't helped that at least some owner's manuals provide contradictory information!

Howdy, Stranger!

Quick Links

Categories