How to Check Electric Brakes on a Horse Trailer

Electric trailer brakes are designed to slow a trailer and usually cannot lock up the trailer's wheels when it's loaded. That's why It is important to tow with a heavy duty vehicle. The tow vehicle supplies the power to operate electric trailer brakes. When voltage is sent to the trailer brakes, an electromagnet mechanism in the drum applies the brake. Most trailer brake failure is caused by little or no voltage to the brake magnets. Broken and corroded wires or wire connections are the common cause and can be found on either the tow vehicle or the trailer.

Instructions

Preliminary Testing

1

Hook the trailer to the tow vehicle and connect the trailer plug.

2

Apply the emergency brake in the tow vehicle and block the trailer wheels.

3

Spread a ground mat or a large piece of cardboard under the trailer.

4

Go under the trailer with at 12 volt DC test light and a continuity tester. Use the 12 volt test light and test the two wires going into each of the brake backing plates for power while someone applies the the trailer brakes.There must be power in one wire going into each baking plate for the electromagnet to apply the brakes.

5

Mark the wires that light the test light on each backing plate as the positive and the other wire as the ground.

6

Test the ground wire going into each backing plate using a continuity test light by grounding the continuity light and probing the ground wire. If the ground wire is properly grounded the light will light.The continuity tester gets its power from an internal battery.

Dymanic Brake Check.

7

Adjust the trim wheel on the trailer brake unit to the maximum setting. The brake unit is normally mounted under the dash board of the tow vehicle.

8

Drive the trailer to an area that has loose gravel.

9

Apply the trailer brake lever, but not the tow vehicle brakes while driving slow. If the brakes are working properly the wheels should slide, or a drag should be felt. The trailer should be empty when performing this task.