I'm having trouble with the wiring on my 16' flatbed trailer. I have a hopkins brake box plugged into factory tow harness, and have the trailer plugged into 7-pin rv plug. All lights are fine, but the brake box shows "trailer disconnected". Ive read in other threads that the box doesnt care what wire is hooked to the "brake" connector on the truck plug, and having swapped both wires to the "brake" connector with the same results, I'm confused. What am I missing? There is a yellow and a brown wire coming from my trailer brakes... Any help is greatly appreciated.

Thanks, Steve

 

I'm sure someone else will step of but from what I know about them..
Make sure you have the power to the plug put a meter to the plug on the truck and have someone hit the brakes to see if you have power to the rear of the truck.
Next check the trailer and make sure you have a ground going to the plug do not trust the ball to be you ground.
Check to see if you have power going back to the brakes at the wheels.
So now you have traced all the power back to the trailer brakes and you have power make sure the ground wire on the brake backing plate is grounded. Still no power then you need to rebuild or try another magnet.
If I remember you can plug in 12v to the plug (brake) and - plug (ground)to the trailer and have brakes but check with someone first. I hav never had all the brakes stop maybe one magnet will stop but not all without a short.
If your wire runs inside the axle it may be shorted, pull it out and rewire it.
A lot of the guys hav been having problems with that.
Let us know more about what you find.
Also try your truck on another trailer if you have on will tell you quick if its the truck/box or the trailer.
Also by Both I think the are talking about the magnet it has two wires off of it and it works either way. not the brake box wires.
Jon

 

Thanks for the reply. I have checked voltage at the truck plug, and do get 12v, and I did add a ground on the trailer that goes to the - on the truck plug, so I have nice bright lights, and I dont think I have a ground issue. I'm basically learning about trailer brakes, so I dont know a lot about how they work just yet. Is there somewhere that I can check for 12v on the brakes themselves without having to open the insulation on the wire and check it there? The wire does run thru the axle tube, and I did read how some guys have some rub thru. So, should I start by just rewiring the brakes outside the axle tube and see where that gets me? As a side note, should I worry about pulling a loaded trailer (around 3K lb load + trailer) without operational trailer brakes? The brake box is new, and is plugged into the factory harness, so hopefully I dont have any problems there. I dont have any problems with the lighting, so I think it is just a brake issue, and I think it is with the trailer.

 

I had brake problems with our camper last year when I bought it (used). Turned out to be faulty wiring running through the axles. I rewired it and it was fine.

The easy way to find the problem is to cut all of the wire connections to all four brakes and then rewire the one closest to the main wiring harness. Then check to see if you have a connection on the control box and the brake should make a humming noise when you move the manual slide on the brake controller. Then just reconnect one brake at a time making sure that you have a connection and adequate voltage each time you wire a new one in. This will help you isolate the problem with is either a bad connection or a corroded wire in the axle. You won't get a full 12 volts back to the brakes. My brake controller puts about 4.5 volts back to the brakes when I move the manual slide. I know this sounds like a lot of work to mess with, but it is easier than chasing the problem.

 

Easy way to check if the trailer brake magnets are working is hold a magnetic compass close to each magnet while having someone step on the brake pedal. If current is flowing thru the magnet the compass needle will move.

 

Also, don't worry about a 3K load. Truck will handle it just fine. Just drive using some common sense.

 

ok, after a little more digging, this is what I have come up with. (and a correction to earlier post, I have 3v at the plug on truck, not 12v.) So, I have 3v at the plug on truck, and 3v on wire going to brake magnet, all looks good at this point. When I put brake/hub assy back together, I still get an error on box that shows "trailer disconnected" and still no brake operation. wheel spins freely. Is this a candidate for "rebuild"? If so, what does that entail? The shoes look serviceable, is it possible to just replace the magnet(s)? I tried the magnet trick, and the needle moves toward the magnet, but I'm a little confused about why that is the case, but I still have no brake operation and error on brake box/

Thanks for all the help, its greatly appreciated. This site has been very informative and helpful to me...

 

if you have a 12v test light put it between the brake line (#2 blue bottm left) and ground (#1 white bottom right)at truck plug with trailer disconnected and your brake box should read connected (or ok), if it still says no connection then your brake control maybe bad. also test light should come on when the brakes are applied.