Not Getting Full Voltage at Trailer Brake Magnets After Installing New and Larger Brakes

Updated 09/28/2016 | Published 09/27/2016

Products Featured in This Question

Draw-Tite Activator IV Trailer Brake Controller - Up to 4 Axles - Time Delayed

(357)

$103.31

10 Gauge Wire - Blue Primary - Per Foot

(104)

$1.89

Question:

I have 2 new 5200lb axles with 12inch brakes now under my tandem car trailer. I WAS running a single axle with 10inch brakes before this up grade I have a adjustable brake controller, I believe its a Draw Tight 5100. At full adjustment on the controller , I have 5.6 volts across all the magnet connections. And 6.7 Volts if I go hot feed wire to frame to ground it. With the wheels off the ground. All appear to work properly. With a unloaded trailer off 2000 lbs. I am unable to get the rear axle brakes on either side to lock up and skid the tires even on just dirt. The front I can lock up on any surface. I have gone back and adjusted the new brakes. Same results. I have also replaced the wiring that jumps from the front working axle to the soft operating rear axle to make sure all connections were fresh and solid. Should I be running separate wires to the trailer plug and not jumping from the front axle ? Or what ???

asked by: Mike T

Expert Reply:

Usually on tandem axle trailers the brake magnet wiring is jumped from the front to the rear axle. You can try it other ways to see if that helps. I recommend grounding the brake magnets near the brake assemblies to avoid any voltage drop off. Make sure the ground locations are clean and free of corrosion.

You didn't mention the wire gauge being used but for electric trailer brakes we recommend 10 gauge such as # 10-1-1 sold by the foot.

You can also check the trailer and vehicle side connectors to make sure they are clean and free of corrosion inside and out.

Another thing to check is the brake controller. You went to more and larger brakes so if you kept the brake controller settings the same then that could be another problem.

expert reply by: Michael H