Troubleshooting Trailer Brakes With Low Voltage

Updated 09/16/2025 | Published 04/19/2018

Question:

My trailer light work on the trailer but my electric brakes do not work do they have a fuse that controls them or could it be one of the wiring in the inside of the Hub I have current to all of the wheels at one point five

asked by: Frederick

Expert Reply:

If you are only getting 1.5 volts at your brakes then there is an issue, but there is not a fuse that controls the brakes. There are a number of possible issues so you will need to find out if the issue is on the brake controller, truck, or trailer. To test the brake controller, sever the blue wire a couple inches from the back of your controller. Then use a circuit tester such as # PTW2993 to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override; if it shows power at idle then there is an issue with the controller, and it will need to be replaced.

If the controller tests fine, reconnect the blue wire and move on to the truck side trailer connector. Often, corrosion or dirt may be the cause of a short in a trailer connector that could be hampering your wiring. Check the plug to see if there is any type of corrosion built up that may be hampering its functionality.

You will also want to test the brake output pin on the 7-way socket; it should only show power with the manual override. If it shows power any other time then there is a short somewhere between the connector and the brake controller you will need to find.

If the truck side checks out, then it could be the wiring to the brake magnets or possibly the magnets themselves. Inspect the power wires to the magnets and look for wires that may be pinched or otherwise damaged and fix as necessary. You'll also need to make sure all of the ground wires, including those coming from your brake assemblies, are attached to bare metal surfaces and free of any paint, dirt or corrosion.

You'll want to visually inspect the magnets; if you can see the copper windings coming through the magnets will need to be replaced. To test the magnets, you can follow the help article I have linked. I have also attached some help articles for you to check out which should be useful.

expert reply by: Kyle S

Frank

9/16/2025

I replaced my magnet on all fours tires and still no trailer braks. I hit the gain and can hear the brakes engaging. And I also adjusted the brakes. Do you have any ideas what it could be. Low voltage? Or maybe a bad ground

Jameson C.

9/16/2025

@Frank Could be a bad or weak ground or also if the wire gauge wasn't heavy enough it wouldn't be able to carry enough current to activate the brakes so make sure you are using 10 gauge wire like part # 10-1-1 as well.