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Troubleshooting Weak Electric Drum Brake Operation


I recently installed a Tekonsha Primus brake controller in a Jeep Grand Cherokee along with Dexter 10inch Nev-R-Adjust Electric Brake Assemblies for 3.5K Axles. The Primus setup instructions say to set the controller at 6.0 then run the tow vehicle and trailer up to 25mph and stop the vehicle and trailer by pressing the controller bar and if it locks the brakes then back off the assist until it stops quickly without locking but if the brakes seem weak then adjust the setting upward. Well I have adjusted the brakes at the drums so they drag slightly when turned by hand and if I set the controller at 13 it’s Max setting it still will not lock the brakes when stopping from 25mph, the trailer loaded weighs roughly 2500#. I know the brakes are operating because I can feel some drag and I can also hear the hubs scraping as I apply the brakes. When setting up the brakes I used a factory kit from Mopar on the Jeep and when I installed the brakes on the Trailer I used 14 Gauge wire and I soldered all connections and I also ran the grounds all the way back to the ground wire that came from the 7-way molded trailer wire connector where it was also soldered. Could it be that the gap between the brake magnets and the face of the drums is too wide which could result in a weak brake response. If so could placing shim washers between the Brake assembly and the Brake plate on the axle be an effective solution, this would move the magnet closer to the drum face. I installed the unit tagged Left Side on the Drivers side and the unit tagged Right Side on the Passenger Side, I can’t imagine why I’m not getting any better response from this setup. Thanks.


Expert Reply:

It sounds like your issue is related to the light wire gauge used for the brake circuit.

A trailer that uses electric drum brakes, even if it is a single axle trailer with only two brake assemblies, should be wired with no smaller than 12-gauge wiring. 10-gauge is preferred and is essential if the trailer has multiple axles all with electric brakes.

We recommend using our # 10-1-1 primary wire for brake circuit applications. This should correct your issue.

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