Troubleshooting Low Voltage Output From Brake Controller On A Triple Axle Trailer
Question:
Im having trouble with my trailer brake voltage output. Trailer is a 3 7k lb axle zieman, all 6 wheels with electric brakes with modern self adjusting shoes. Wiring is relatively new and not corroded. Pull vehicle is a 2011 f350 with factory brake controller. Everything works correctly except when I plug in my trailer plug, the voltage to my brakes s around 4 volts. I clamp the trailer brake controller and turn the gain up all the way. I test voltage at the plug in my bed and on my bumper and have ~12V. As soon as I plug the trailer in the voltage s to 7-8V. When I go into the junction box and remove the wire going to the brakes from the post in the box, voltage come back up to 12V so I know its not the plugs on the truck or the wire/male plug on the trailer. I figured a brake magnet was shorting so I tried to isolate the axle it was on. I snipped brake wires going to axle 1, voltage still ped. Snipped wires going to axle 2, voltage still ped when I plug the trailer in. Snipped wires going to axle 3 so now no trailer brakes are hooked up and voltage came back up to 12v. I thought that meant there was a short on one side of axle 3 but as soon as I hooked axle 1 back up, voltage ped again. Everything else has proper voltage and works running lights, brake lights, turn signals, charging wire for break away battery. Also, when I leave the brake controller clamped for a while, the trailer brake post in the junction box gets hot. My trailer brake hot wire must have a short but the wires are all nice and new from the junction box to the tail lights. If it was a short in the hub or at the magnets, i would have found it by removing the shorting axle from the circuit. Any ideas?
asked by: Mark
Expert Reply:
Hey Mark,
What gauge wire did you use to run from the junction box to the brake assemblies? If you didn't use at least 10AWG wire # 10-1-1 that could explain the heat build up and voltage drop. I don't recommend leaving the manual override clamped for long periods of time. I recommend reconnecting your brake assemblies, activating the manual override, and then then testing both wires coming from the brake magnets to see if there's voltage on both wires. Only one should have voltage and the other should be grounded. If you're getting voltage then they we either wired incorrectly or they're in need of replacement.
This could also be an issue with the brake controller. I recommend testing it out on some other trailers to see if the issue persists. It could be working fine without a load but as soon as it's reading the trailer it's malfunctioning.
Let me know what you find and we can keep troubleshooting if this doesn't help you find the culprit.
Products Referenced in This Question
Product Page this Question was Asked From
Continue Researching
- Shop: Trailer Hitch
- Q&A: Recommended Trailer Wire Harness For A 2020 GMC Terrain
- Q&A: Recommended Kayak Carriers For A 2016 Ford Fusion With An Inno Roof Rack
- Q&A: Parts Needed For An Over-Under Suspension Conversion On A Boat Trailer
- Shop: Electric Jack w/ Footplate and 7-Way Plug - A-Frame - 25-1/8" Lift - 3.5K - Black
- Q&A: Can Roller Bunks Handle a 3,200 lb Flat Bottom Boat
- Shop: Curt Trailer Hitch Receiver - Custom Fit - Class III - 2"
- Q&A: Does Stay-IN-Play Duo Flat Tow Brake System Work on 2018 Chevy Equinox
- Shop: etrailer Trailer Hitch Receiver - Custom Fit - Matte Black Finish - Class III - 2"
- Shop: TorkLift SuperHitch Original Trailer Hitch Receiver - Custom Fit - Class V - Dual 2" Receivers
- Q&A: Does Torklift Hitch # TLF1002 Fit 4WD and 2WD Versions of 2011 Ford F-250
- Q&A: Torklift Superhitch Options For 1999 Ford F-350 Super Duty
- Shop: etrailer Hitch Pin Alignment Collar for Hitch Accessories - 2" Hitches
- Article: How to Choose the Right Trailer Hitch Class
- Search Results: hitch
- Shop: Trailer Wiring
- Video: Choosing the Right Trailer Wiring
- Shop: Universal Installation Kit for Trailer Brake Controller - 7-Way RV and 4-Way Flat - 10 Gauge Wires
- Shop: Fifth Wheel Hitch
- Search Results: trailer jack
- Article: Brake Controller 7- and 4-Way Installation Kit (ETBC7)
- Video: Choosing the Right Brake Controller
- Shop: Suspension Enhancement
- Shop: 7- and 4-Pole Trailer Connector Socket w/ Mounting Bracket - Vehicle End
- Search Results: brake controller
- Article: My Trailer Hitch Doesn't Fit
- Video: Choosing the Best Fifth Wheel Hitch
- Search Results: trailer brake controller
- Shop: Brake Controller
- Video: etrailer Electric Jack with Footplate and 7-Way Plug Review
on Wiring
Mark M.
4/3/2024
Thanks for the quick reply and good idea. I didn't want to re wire all my brake magnets but I did test voltage on one of them just before the wires enter the hub and got the same reading as testing at the junction box. I have two zieman trailers so I hooked up to the other one today and found it did the same thing...voltage drops 3-4 volts as soon as I put the wire going to all the brake magnets back on its post in the junction box. This made me thing the truck was the issue. Tested both trailer plugs, both acted the same. No blown fuses, no trailer warnings on dash. Pulled up the work vehicle which is a 2015 dodge 3500 just to confirm that my ford was the issue. The dodge acted the same. I'm fully stumped now. When I push on the brake pedal I get 0V to the junction post. When I squeeze the brake controller the absolute most I was able to get with the truck running was 11v, most of the time ~9v. So both trucks and both trailers drop voltage to under 10v when I plug the brakes in. If I take the brake wire off it's junction box post, the truck thinks I disconnected the trailer but will then have 12-13v. Not sure what to try now.