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One Side of Trailers Electric Brakes Locking Up Intermittently


One of my trailer brakes is locking up randomly while towing loaded and I cant figure out why. If it was the controller, both brakes would have the problem, but this is one side only. Detailed story follows: Bought a used 2-axle 2007 Aztek 20 foot enclosed trailer three months ago with electric brakes on the front axle only. Dexter 3,500-lb E-Z Lube Axles, #84 spindles, 10 inch x 2-1/4 inch drums. Installed new Tekonsha N90160 controller and new wiring and 7-pin receptacle on tow vehicle. Trailer weighs about 2,000 lb and cargo weighs 1,800 lb. PO said brakes not working, he had a shop replace the brakes with B10E-21/B10E-22 AKEBRK-35-SA. The shop supposedly repacked the bearings, but on inspection I saw they just put new grease on top of old using the EZ lube fittings. They did not take remove, clean, and inspect the bearings on any hub, and did not mention that both idler bearings were clearly bad, rough when spinning by hand. So, I believe it is easily possible the shop did something wrong in installing the brakes. The RF brake locked up ~300 miles after new brakes installed, happened at low speed ~30 mph. Ground the tire to the cords before I realized it. Tire shop was unable to free the wheel. I remove the castle nut and after taking the outer bearing off the drum freed up with a big popping sound. I inspected the brake and did not see anything particularly unusual. No grease on brake shoes, no broken springs. The magnet did seem to have a lot of wear for so few miles. All photos at 300 miles since new brakes. Referring to, I tested brake controller output blue wire, it was within the correct range of 7.5-8.2 amps at 12-13 VDC. With ammeter in series, connected magnet to 12V battery and the reading was within the correct range of 3.2 - 4.0 amps at 12-13 VDC. Energized the magnet and verified it attracted steel objects, and tested for a short but found none. Brakes seem to be adjusted correctly, a very slight drag when spinning by hand. Inspecting the wiring harness, I did find some small breaks in the brake wire insulation, and also found the trailer ground was questionable. Replaced the wire, fixed the ground, and put over 1000 miles, mainly freeway, on the trailer with no incident. Then yesterday, the RF wheel locked up again pulling away from a stop sign. This time, backing up freed the wheel. Inspected brake again and didnt see anything unusual, but noticed the wear surfaces between the brake backing plate and brake shoes had never been lubricated. Put some axle grease on the six wear pads, being careful not to get any on the shoes. Drove about 30 freeway miles with no problem, then when starting out from a stop light the RF locked up again. Short of replacing the brake assembly, what could be the problem and how can I fix it? Thanks in advance....


Helpful Expert Reply:

Thanks for that level of detail, as it takes a lot of the guesswork out. And you did literally everything with testing and fixing what were likely some issues, but not specifically ones contributing to this. I am very confident that the problem with the brakes locking up is due to some component being faulty within your trailer suspension.

There are a few reasons for this; first is everything you did regarding testing the brakes and doing some repairs with the wiring; also when just one side of the brakes lock up, suspension is very frequently the cause apart from a funky ground wire issue, and finally, the fact the shop just put new grease in just on top of the old and did not inspect the bearings or hub is very telling. A bad suspension component - likely the spindle in your case - can mean that side is off-kilter and the brakes are working more and locking. You also said the drum freed with a big popping sound - it should have slid off easily, which is why I think it's the spindle.

So I recommend having a trailer dealer/shop take a complete, thorough look at your suspension, particularly the spindle, but also the springs and axle, to see if anything needs replacing. If so, you will need a spindle that is the right fit for your trailer's axle, like the 3,500 lb # TRU24FR.

I'm sure this isn't what you were wanting to hear, but it is definitely the most likely scenario for you. If you do wind up needing replacement parts, I'll go ahead and link below our spindles, hubs, springs, and axles for you.

helpful expert reply by:
Kyle S

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