Will a Dead Battery In the Breakaway Box Cause Trailer Brakes to Not Disengage?

Published 10/26/2016

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Replacement Breakaway Switch for Bright Way Trailer Breakaway Kits

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Loctite Bulb, Lamp, and Electrical Connection Dielectric Grease - 0.33-Oz Tube

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Hook Probe Circuit Tester

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Question:

I have a horse trailer that is not used often. The last time I used the trailer I hooked up very early in the morning. Had a problem with the lights coming on at first but, when I had the trailer wires properly hooked up I was ready to leave the property and when I turned the lights on the tow vehicle on the trailer brakes would not disengage. When I unhooked the trailer light cable the brakes disengaged and I was able to drive but I didnt have any trailer lights. After driving in the dark for about 20 miles I reattached the light cable and the lights and brakes worked for the remainder of the trip. The question is whether a dead battery in the Breakaway box would cause the trailer brakes to not disengage?

asked by: Ken L

Expert Reply:

A dead battery would not be the cause of your brakes not disengaging. A dead battery would have the complete opposite effect on your brakes. A dead battery wouldn't send the electric signal to engage the electric brakes and no electric signal would mean no brakes at all from the breakaway standpoint, but you will still have brake signal from your brake controller.

When you connect your tow vehicle, that will send signal to your trailer brakes only when the brakes are engaged on your vehicle or with the manual override on your brake controller. It is interesting that other systems didn't work and then eventually did...this leads me to believe you may have a short somewhere in your wiring system. I would suggest you charge your breakaway battery so that it works in a crisis situation and use a circuit tester like # PTW2993 to test all your connections at the vehicle side connection first and then your trailer. Make sure to use a good ground when testing and make sure you have a good ground connection at your trailer for your wiring that is clear of debris, rust, or corrosion.

If there is moisture, like from a thick morning dew, or any corrosion inside of the trailer connector that could keep the lights from working properly. I would suggest you put dielectric grease like # LT37534 on your connection terminals to seal out moisture and prevent corrosion.

expert reply by: Jason S