Troubleshooting Electric Brakes That Energize When Not Connected to Tow Vehicle

Updated 02/04/2019 | Published 02/01/2019

Products Featured in This Question

Replacement Trailer Brake Magnet for 12" Brake Assemblies

(40)

$29.03

Replacement Breakaway Switch for Bright Way Trailer Breakaway Kits

(170)

$9.94

Ring Terminal - 12-10 Gauge Wire - 3/16" Ring ID

(71)

$1.17

Wiring Kit for Hydrastar Electric Over Hydraulic Actuators

(12)

$87.55

Question:

Got a jayco expanda 2011 caravan and the brakes are making a loud buzzing sound but they are not connected to the car?.... the emergency safety pin thing at front seems to be intact too..... what could be causing this???

asked by: Paul W

Expert Reply:

Trailer electric drum brakes do make a humming sound when their magnets are energized with power from a trailer brake controller. This is normal behavior and it is usually possible to hear the energized brakes from about a foot away.

If your brakes are being energized when the trailer is NOT connected to the tow vehicle this indicates an issue in the trailer wiring. Something is allowing 12V power to reach your brakes when it should not. Since the trailer is disconnected from the tow vehicle this means that either the trailer breakaway battery or the onboard auxiliary battery wiring is somehow allowing power to get to the brakes.

This could be something as simple as a wire rubbing against the trailer frame and causing a short. Or it could be a result of corrosion within the trailer's plug that is allowing power from one circuit to reach the brakes. You can try disconnecting the batteries, one at a time, to see what will stop that power from reaching the brakes. Once you determine the source of the power this will help narrow down the items you need to check.

You may need to repair or replace a damaged wire, or possibly the breakaway switch if it is bad, with a replacement such as # 3802348. All replacement switch kits are linked; you can use any brand since they all function the same way. An article is linked to help you test your setup.

If you find that you need a new 7-way you can use part # HS381-9000 which includes a junction box that lets you make your connections to the existing trailer wiring using ring terminals # 44-5310A.