I’m about ready to throw in the towel on the trailer brakes. I’m officially out of ideas as to the solution to the lousy brake performance.

When I first got this trailer, if you set the brake controller on max, it would flat spot all 4 tires even with the trailer heavily loaded. Now, while the brakes do work, they are nothing like they were. They just dont pull down the truck like they use to. With racing and several car shows I want to attend this year, I’d like to get this fixed.

I have checked individual wheel magnet current draw and resistance. They are 10 inch drums, according to the specs I have found the should measure 3.0-3.8 ohms. Each wheel fails within that range. I then checked current draw, they should each pull 3-4 amps. Once again, they all fall within the spec. I have replaced every wire in the brakes (12 gauge from the trailer junction box to the axles, then 14 gauge to each wheel) the ground wire is also 12 gauge, plenty for the expected 16-20 amp draw. There are zero scotchlock electrical splices, where splices are needed i soldered and heat shirked each connection. The brakes are adjusted to where there is a slight drag when splinting the wheel. The brake hardware is clean and lubed. If you spin the wheel by hand and have a helper pull the emergency brake away pin, each wheel immediately locks.

After going thru all this, I assumed the problem must be either with the truck, or the brake controller itself. I eliminated that possibility when moving another trailer. I had the brake controller set on kill (the only way to get somewhat acceptable braking performance with my trailer) the brakes locked immediately with a different trailer.

I’m out of ideas. At this point, I’m ready just to buy new brake backing plates. That will give me new brake shoes, hardware, and magnets. If that’s what it takes to make this right, I have zero problem with that. Is it possible for them to test according to spec, and still be weak magnetically??

I just don’t understand how things can test mechanically AND electrically fine, but not work. Brakes are something that needs to work correctly each and every time.

Any ideas? What have I overlooked? Thanks!!

 

Did you check with an auxiliary battery or the truck electrical system ? I wonder about a problem with the trailer tongue coupler or trailer wiring plug on the trailer.

 

there is a auxiliary battery that I use to power a winch, and some accessory lighting. I have replaced the trailer plug itself, and there is a seperste ground wire, the trailer doesn’t rely on the coupler to provide a ground.

As I mentioned, there are no problems with the truck pulling another trailer, and my trailer brakes work the same with my truck verses any other, it’s definitely a problem with my trailer.

 

I had the same issues with mine. I put on new backing plates with new brakes and magnets then replaced the drums. Also replaced the trailer plug. Works like new now. The trailer mechanic told me the drums had to be smooth and clean. It would cost more to turn the drums than to buy new. Like you I was going crazy trying to get it to stop properly. Good luck.
Rick

 

Matt - I feel your pain. I know you realize not all trailers follow the same wiring schematic with reference to wire colors. It could be the backing plates, I know you just changed out the plug/wires - it wouldn't hurt anything to perform a double (triple) check on the wiring paying careful attention to the blue, black & white wiring. If it were me, I'd remove the accessory wiring & winch from the wiring just for the time being (since those are both add-on accessories) to see if you can get the brakes working without the accessory wiring & winch possibly causing an issue.

As I mentioned, pay careful attention to the blue, black & white wiring - especially in relation to the breakaway, ensuring you have correct wires. IIRC, the blue is always the brake/magnet wire (ensure you have a independent white [ground] wire from the breakaway that is "looped" into the frame [ground] and runs into the brake ground).

As suggested, I'd remove your auxiliary accessories/connections & the winch (for time being) to see if you can get the brakes working first, then add the auxiliary/winch.

At the risk of thinking I'm just tossing up yet another wiring diagram, it never hurt me to review as many as possible since I've been down this road myself with several trailers (some of which I added auxiliary accessories), as well.

Good luck - I really do feel your pain.

https://www.randpcarriages.com/help-...n-your-trailer

 

This might be a solution. I don't know how you measure magnetism specs with conventional tools we probably have. You've checked everything but the magnets. Its possible the magnets have lost enough power to cause your problem.

 

Even after I replaced the shoes and magnets, I was not getting enough brake. with the old drums. After replacing the drums everything worked ok. I spent over a month working on this trying different things until I got it right. The trailer is over twenty years old so with new tires it is back in tip top shape. Hang in their Matt I know how frustrating this can get.
Rick

 

other than a resistance and current draw test, I’m betting manet testing is beyond the scope of 99% of the DYI and RV service centers. I’ll probably replace the backing plates next and see what happens.

As for the winch and accessory lighting, they are connected directly to the battery. They are not connected in any way to the trailer wiring.

 

Matt,

I need to say up front that I have no experience with electric trailer brakes, but I am familiar with hydraulic drum brakes.

Your electrical measurements checked out OK, so that indicates the magnets are doing what they are supposed to do. Assuming that is correct, treat them as drum brakes and look for the same things as conventional drums.

Things to consider:
How are the shoes - worn or glazed?
Are the drums glazed or oily? Worn beyond max diameter?
Is the hardware/springs in good condition?

 

Plenty of brake shoe life left. The brake hardware is clean and free to move, and as I mentioned they are adjusted to provide a slight drag when rotated.