Troubleshooting Trailer Brakes Locking Up Without Applying Vehicle Brakes  

Question:

Expert Reply:

The brakes on your new RV trailer can be activated either by the brake controller or the trailer's own on-board emergency breakaway system. I have not heard of an issue with the Echo # C51180 before now, and while it is possible the unit has an internal malfunction I suspect the problem is more likely to be in either the trailer's breakaway system or within the 7-way wiring on the Audi or the trailer.

For the trailer brakes to lock up without you pressing the brake pedal they would need to get a full 12V signal from somewhere. You might merely need a new breakaway switch like # FA80-00-2040 or you could have trapped foreign material in the 7-way socket (or in the wiring the connects to it) that is allowing the 12V auxiliary circuit to become bridged to the brake circuit. You can also test the 7-way without the Echo installed. These possibilities seem unlikely with a new trailer towed by a 2019 Q5. If I had to take a shot I would look at the breakaway system as the cause. New breakaway switches are inexpensive and easy to install (only two wires).

If you have a circuit tester like # PTW2992 you can test the brake output pin on the Echo (the one at the 5:00 position) while the trailer is disconnected. Use your phone to engage the Echo's manual control. You should detect brake power with the manual engaged but NOT detect it without the manual control engaged. If you find brake output on the Echo without using the manual control then the unit itself indeed has an internal fault.

You can refer to the linked articles for help with testing and re-installed new breakaway parts.

expert reply by: Adam R

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Mark H.

5/16/2020

Adam, I would like to follow-up to Larry's question and your answer to it. Today, I was towing my 23' 2012 Airstream to dump tanks. I tow with a 2011 BMW X5 and a Tekonsha Prodigy RF break controller. My trailer brakes locked up 2 separate times about 3 minutes a part and neither time was I applying the brake in the tow vehicle. I was driving about 60mph on interstate, and it was like a HUGE trailer sway set in - major fish tailing left/right like I have never ever experienced before. It was like the trailer brakes were fully engaged. The second time it happened, I was going a little slower which is a good thing as the lockup was worse/lasted longer. The car was for all practical purposes out of control, shaking violently, and I thought I was going to be overturned. I see where you mentioned about the Emergency Breakaway Switch, and indeed the way the trailer was stopping, that is what it seemed like was happening. However, I though the Emergency Breakaway only engaged if the pin was actually pulled out? My pin is still intact. Thoughts on this? I got to the dump station and drove back 15 miles very carefully with no other issues. Your thoughts would be most appreciated. As part of my trouble shooting, I am going to order a new Tekonsha Prodigy from e-trailer.

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Chris R.

5/19/2020

You're right that the pin on a breakaway system needs to be pulled for it to send back power to the brakes, but there might be some damaged wiring on the system that's causing a short - possibly an exposed section that's touching bare metal or a neighboring wire after a bump in the road (which is maybe why it only happened a couple times). I would definitely try to inspect the trailer wiring as much as you can, looking for anything that needs to be repaired/replaced before your next trip. If you don't find anything visibly wrong, just let me know.

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