Trailer Wiring Fault Message on Tow Vehicle and Brake Controller Shows Trailer Disconnected
Question:
Mobile suites 36 ft 5th wheel. I just replaced all four wheel bearings and brake assemblies. They are wired almost exactly like your diagram except I crossed from driver side to curb side at each axle. Brake assemblies are Dexter. 7 pin ford factory pin has a green power and white ground at the 7 and 5 oclock position on the plug in. The trailer plug cable has the white spliced into a white ground wire and the green spliced in to a black power wire. The white and black then run as a sheathed pair down the driver side of the trailer. The assemblies are connected to the white and black without regard to power/ground, I understand it makes no difference which wire from the assembly goes to white or black. Once I had everything hooked up I set up to burnish the brakes as described in the literature from Dexter. Soon after I began getting a WIRING FAULT ON TRAILER message. I found a fault on the front axle and corrected it. I found no other fault. Still I get the fault message at times and the TBC trailer brake controller will not activate the brakes. This is an intermittent condition as sometimes it will se the trailer and work as it should and other times it will give me a trailer disconnected message followed by the fault message. Finally, when hooked up and in use the brakes seem to work. The trailer is heavy and I would know if the brakes werent working. Brake pedal cannot be checked until truck speeds exceed 12 MPH. In checking the wiring I have continuity between the white and blue wire. That seems strange but I guess if the magnets are wired without regard to polarity that would be correct. Am I right about that. I am certainly open to suggestions from an expert, Thank you
asked by: Stanley
Expert Reply:
For starters, you are correct in that the wires on the braking assemblies are non-polarity specific so that basically means you can use either for power or ground. Now with that being said, it really sounds like you have a short on the brake output wire that runs from the braking assemblies all the way up to the trailer connector. This is going to cause intermittent brake function as well as tricking the vehicle/brake controller into thinking the trailer has been disconnected.
The only way to correct this is to trace it back from each braking assembly all the way up to the trailer connector. I would pay close attention to all of your splices, especially where the brake assemblies tie together and then run up to the trailer connector. If you did not replace the brake output wire where it is tied into the braking assemblies and then ran to the trailer connector you will want to do so with part # 10-1-1 which is a 10 gauge wire.
The issue could also be with the brake outwire wire that runs from the vehicle side trailer connector to the brake controller so you will need to check this as well. If you have a seperate trailer/tow vehicle you could easily test this theory. If you are not able to find the short then you may want to take the trailer to a local mechanic as the wiring faults can be hard to find if you just installed the wire yourself. The reason for this is because you may overlook something that you think is correct when in all actuality it could be the issue you are having.
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on Wiring
Teddy J.
7/21/2020
While driving my truck and not pulling a trailer my wiring fault on trailer came on. I'm not sure what it means like I said my camper is t hooked up to the truck at the time. I cleared the code but when I get Back in the truck it comes on after about five minutes of driving.