We have a 1996 Sundowner stock trailer that gives us a “Wiring Fault” notice on our truck computer when hauling horses. We don’t get the fault when the trailer is empty and we don’t get the fault with any other trailer so we’ve ruled out the truck as the problem. Twice we’ve gotten a “Trailer Disconnected” fault. We’ve had the trailer looked at by a couple different places and no one is sure what the problem is. I’ve tried calling Sundowner and they haven’t responded to my messages. Has anyone else had this problem?
When you get the fault turn on all the lights, do a walk-around and see what isn’t working. Also pull forward slowly and manually apply only the trailer brakes with the electronic controller and see if they grab. You can also use a single jumper cable ( for jump starting batteries) clamped to the trailer tongue and the truck bumper or hitch as an extra electrical ground between the two vehicles and see if that eliminates the fault warning.
Since the fault only appears when you have horses loaded it indicates the problem comes with axle spring compression, so those are the areas I would trace and inspect the wiring harness.
Most trailer electrical problems turn out to be a bad or intermittent ground wire. ~FH
just a guess on my part but check all electrical ground connections of the trailer’s wiring harness and all electrical connection points (lights normally are just power in then ground return) as the wiring connection fitting are not aluminum and there can be corrosion develop between the fitting and the aluminum frame of the trailer
My guess is the truck’s computer is seeing a request from the trailer’s harness of a power load that is higher than expected or there is increase resistance in a connection that is not allowing for the DC voltage to return to the truck.
purely a guess on my part from seeing problems with house wiring from the 1970s when aluminum wiring was used for a period of time as a cost saving. Problem was many electrician used the wrong connectors thus cause fires.
I have a 1998 and don’t have that issue. I DO have some issue w/ the battery for the interior trailer lights when it isn’t hooked up. Other than that, I love it and it has been an awesome trailer for me.
It sounds like we are going to have the trailer rewired. Our mechanic thought he might have solved the problem a couple weeks ago but we hauled horses yesterday and got the fault again. Apparently where the wiring is is rather tight and the wires are not very long so not much to work with. Hoping this fixes the problem. Unfortunately we only get the fault when moving so we can’t get out to check lights when it goes off:)
Sounds like exactly the same problem I am having with my new used trailer. It is a 90 Logan though. Everything works perfect when tested empty, but put a horse in it and the faults start happening. Stop the trailer and it works again. Start to go and you get faults again. Took it back to the guy who installed the new brakes and they can not find a thing… I am still not comfortable trying to use it since we have still not found the problem…
This is an old thread but I just repaired a friend’s trailer. Three different wiring faults in the ground circuit. Loose wire, bad connector, and mis-wired trailer plug. Each time, I though the problem was fixed, but the lights would fail again later.
The trailer ball would act as the ground until some movement would break the connection. To isolate the ground, hook up a jumper cable between the tow vehicle and trailer. Make sure the clamps are biting on to bare metal. If the problem is gone… You have a grounding issue. Unhitch the trailer & jumper cable, but leave the electric cable connected. Start tracing …
Thanks for the info, hosspuller. We ended up having the trailer rewired. Turns out it was a bit of a mess and now it works great!
