Trailer wiring issues

I had the same issue. Sometimes you have brakes, sometime you don't. My problem was a bad ground at the pin box and shorts in the wires that ran through the axles. Even though the the trailer was basically new, there was enough surface rust on the inside of the axle to rub away the insulation and cause a short. There was a broken grommet that allowed for another short.

I ended up ripping all of the brake wiring out and rewiring using the star method. Wires that needed to run across the axles were moved to a section of PVC conduit mounted to the backside of the axles. The wires that ran through the underbelly were encased in flex conduit.I went ahead and upgraded the wires to 10 AWG. The none weatherproof pin box that used wire nuts was replaced with a weather proof one that used bus connections.

Check the wires on the inside of the drums to make sure there's no shorts going on in there. Sometimes the clips that retain the wires fall off and the wire rub itself raw against the moving parts. The insulation on the wires can burn off as well and cause shorts and failures.

Similar issue on my Bullet Premiere 31BHPR... I'd get "Trailer Disconnected" errors and sometimes I'd brake and the brakes would lock and burn rubber.

After much digging it seemed to be a ground fault between the trailer and TV. To test I took a jumper cable and cable tied it to the tongue and put one clamp on the copper propane line and dug the teeth of the other into a nut on the hitch. Bingo! no more problems unless I forget to attach the jumper to the hitch when I hook up.

I had that issue last summer with both my old and brand new truck.
When we couldn't figure it out we took it to the shop.
Turned out to be 3 of the 4 magnets burned up causing the system to short out.
Once fixed everything worked fine.
You can search for my post under my name.

Joe Williams wrote:
Hello again folks! Here's my problem: when dragging my bumper pull down the road, sometimes I lose my trailer brakes.

The OP has a 23-foot TT Trailer which he likes to call it a "BUMPER PULL".. That is the way I read his response.

I carry one of those 7-way Adapter testers that plugs into the truck side tow connector... This is great for determining if a fuse has blown on the truck side for the safety lights on the trailer but I have never really used it to determine if there was a intermittent connection for the brake control voltage.

Google image

Each brake magnet is suppose to draw around 3AMPS DC current when 12VDC is applied to the electric brakes... This would be 6AMPS for a single axle or 12AMPS for a dual axle. You might be able to rig up something to measure this and wiggle wires while watching the DC current meter... Another way to test if the electric brakes are engaged is to use a camping compass up close to each brake magnet... This will deflect the compass when the brake are applied. Again you may be able to wiggle some wiring while watching the compass when the brakes are applied.

I never did like method the trailer manf runs the wires inside the axle housing to get to the other side of the trailer. Always thought that would be possible failure point of scraping the insulation of the brake wiring over time... I imagine this would be a difficult item to replace as well...

My trailer brake wiring also has several places where wires are twisted together using those yellow twist connectors... Must be common place...

Roy Ken

If you crawl under it and start looking at all the connections you may laugh. I repaired every connection in my system by soldering and heat shrink. Anything exposed to the elements cant just have a wire nut with moisture and dirt getting in it.

I had the same problem and did the same as above. I also chose to wire the brakes in a Star configuration (as opposed to daisy chaining).
I also found a bad ground.

Since making the changes, I've had zero problems.

OP stated that it happens when he drags the hitch. That would indicate that it could be putting strain on the connector.
I do not see how wiring at the axles would cause symptoms.

TexasChaps wrote:
I had this happen on my previous TH... I traced the brake wiring underneath the TH and discovered insulation worn through at the axle. particularly where the wires entered the axle tube to cross over to the other side. movement caused the wiring to short, this was detected by the brake controller.

Same thing happened to my previous camper, wire rubbed at the axle causing it to short. It took 3 trips to the shop with truck and trailer before they found it. Fixed the wire with a bit more length so it wouldn't rub, and never had a problem again.

I replaced all the brake wiring in my old trailer. I chose to wire it in a "star" configuration rather than the typical "daisy chain" which is OEM on most travel trailers. Yes, the brake wires that enter and exit an axle tube are prone to chaffing, either at the entry/exit points or inside the axle tube as the wire is bounced while on the road.

Now, I have a pair of wires from each axle, all terminated on the tongue, inside a box. If one brake fails, I can easily diagnose an electrical fault and more power is delivered to the brakes, also. All the underside wiring is laid in flex conduit.





Yeah, I know I need to get under there and remove rust. :B

You could have a loose connection in the trailer connector. If it is a molded one replace it by cutting cable close to connector.

If you crawl under it and start looking at all the connections you may laugh. I repaired every connection in my system by soldering and heat shrink. Anything exposed to the elements cant just have a wire nut with moisture and dirt getting in it.