Troubleshooting Trailer Brakes That Pulse and Get Hub Hot

Published 04/05/2019

Question:

My dad is having a heck of a time with his trailer brakes. 2016 Grand design 5th wheel. towing with a 2015 Ram 3500. Factory brake controller. Upon returning from a trip last year, found out he had been dragging his brakes for so long, they had completely worn off , less than a year old, less than 5,000 miles. I checked all controller outputs and power references at controller and connector with a meter. All seemed well. Took it to an RV shop for the same. Controller checked out well. Yesterday he asked me to tow it wit my rig to see if we got the same result dragging. Mine is a 2001 F-350, aftermarket controller. I turned my output power all the way down and towed it about 7-8 miles. Brakes were cold to the touch. Adjusted output to where I use it towing my trailer ~85 - 90. his gross = 12,250 lbs/Mine 13,800. Towed about 5 miles ~45-50 MPH. seemed to be going OK. Entered slower zone 35-40 MPH and started feeling the trailer jerk as if we were going through some warps in the road that would normal cause back and forth slack/movement in the hitch so initially no concern. Headed back out and began accelerating slowly. Noticed the back and forth feeling wasnt stopping as should be expected when road is smooth. Then I notice the motion had a rhythm and began to realize it was more of a pulse. I had not touched the brakes at all during the pulses. Decelerated with engine brake no foot brake so all slack should have been gone in the hitch as all trailer inertia should have been pushing into truck/hitch. Still had the pulse. Stopped and felt the brakes after about 3 miles. Surface of the sun hot!! Took off and kept feeling the pulses on on off, here and there. Set controller output to zero and pulses went away. Brakes began to cool. Set the output back up, towed the reminder of the way 3-4 MI, and the brakes were hot again without using pedal.Have confirmed the hot brake issue now with his Dodge and my Ford with 2 different controllers. Any idea why are we cooking the brakes without touching the pedal?

asked by: Jeff H

Expert Reply:

Changing the output setting of your brake controller should not change how the brakes react when the pedal isn't pressed. The controller should be putting exactly zero volts on your trailer brakes without the pedal pressed regardless of gain setting. Did you watch the display of the controller when the trailer was pulsing? Did it show anything like an output setting moving with the pulsing? My theory is there's a mechanical problem on assembly that's getting hot that's causing them to grab and release and it was a coincidence that the issue happens with changes in brake output setting.

expert reply by: Jameson C