Troubleshooting Electric Trailer Brake Assemblies

Updated 04/16/2021 | Published 04/15/2021

Question:

Thank you for getting back to me on my trailer brakes I have a 2018 Chevy Silverado 1500 I’m wondering if the omen reading on my trailer is too high to activate the brakes seeing the brakes worked for a couple of seconds and then stopped the manual controller shows activation but the brakes will not lock up is there a way that I can the ohm reading down to where the vehicle will recognize the brakes? I have a rv with a four wheel braking system and the brakes work fine when connected to my truck

asked by: Carey

Expert Reply:

Assuming that you're speaking of a 10 or 12 inch brake assembly (diameter of the inside of the corresponding brake drum), 3.3 ohms would be correct.

Having a loose or insufficient ground connection at the magnets is the most likely cause for your issue.

With the trailer plugged in, use a voltmeter to check to see if voltage is reaching the brake magnets with the manual switch on the brake controller engaged. Check that the brake magnets are wired properly. Each magnet has two wires exiting it. One connects to the brake output circuit, the other should ground to the trailer frame itself. Make sure this connection is tight, and isn't rusted. I like to sand down a dime-sized area around the ground screw down to bare metal. Use a self-tapping screw and a ring terminal to make the connection. I like to place a star washer between the ring terminal and the trailer frame. The washer will bite into the metal, ensuring a good connection. Finish by hitting the ground connection with a quality rust inhibiting paint like Rust-Oleum.

Check all the connections in the brake output circuit, making sure nothing's loose and not of the wire is cracked or has the insulation rubbed away.

I'll also link to some troubleshooting articles that you might find helpful.

expert reply by: Mike L

Carey

4/15/2021

Mike L.

4/16/2021

Are the brakes functioning, but aren't as strong as you expected? Which brake controller are you using? I've yet to see the brake controller that can't handle 4 brake assemblies. Is voltage reaching the magnets with the manual switch on the brake controller activated with the controller turned all the way up? You should be seeing close to 12 volts at the brake magnets. You'd mentioned something about the brakes not 'locking up'. Have the brake assemblies been adjusted? Once adjusted, the brake drums need to be burnished or broke in before they'll be fully effective. Your trailer brakes should be burnished-in by applying the brakes 20 to 30 times to decrease the speed by 20 mph. Example, once reaching 40 mph use the manual override to slow down to 20 mph. Once at 20 mph, release the manual override and travel about a mile to allow ample time for brakes to cool and repeat the process again. You will need to repeat this process 20 to 30 times. This allows the brake shoes and magnets to slightly wear-in to the drum surface. It's normal for the trailer brakes not to 'lock up'. With the brakes locked up and the tire skidding you won't be getting effective braking. The most effective braking occurs at the point just before the brakes lock up, so this doesn't necessarily pose a problem.