Trailer Brakes Not Staying On
Our travel trailer just started loosing brakes as we travel. A couple of days ago I lost the trailer brakes a couple of hours into or drive. That night I noticed that the plastic pin that connects to ...
Forum Discussion
Since you changed the controller, you may have a real short.
Possible places that may create an actual short in the brake power line.
In the truck:
Check all wires from the controller to the 7-wire receptacle on the back of the truck. Blue is a color often used for the brake hot wire; confirm that it is your color in the harness and trace the harness from the controller to the actual pin in the 7-wire receptacle. If the insulation is skinned, it can touch the frame, which is a short to the controller.
On the trailer:
Is your 7-wire plug an add-on plug to the end of the cable, or is it all one molded cable and plug? If it is an add-on plug, it can be possible a strand of wire in the plug can touch another terminal from a bad wiring job. You can take them apart and check. If it is an all-molded cable and plug, this issue does not normally happen.
I'm not sure about your camper, but most newer campers have a junction box where the 7-wire cable enters and splits into camper DOT lights and the camper brake wiring. They have to connect to the camper blue brake wire in the 7-wire cable; that splice may have a problem.
Trace the camper blue brake wire out of the box all the way to the axle area, and look for skinned insulation.
Inside the brake itself (you must pull the drum to see inside), the magnet coil leads have small clips holding the wire to the magnet arm. Those clips have creaked or were not right from day 1, and the magnet wire gets skinned and can short to the ground. I have seen this; it is not common, but it does happen.
The coil comes loose from the magnet arm due to the clip breaking and gets ground up sideways over time. If the coil wires are exposed, that can be short. When this happens, the magnet is shot, and the magnet arm can also be bad. I have seen this too.
Then there is the worn insulation on the hot wire inside the axle tube. This is a classic failure mode. This is hard to test unless the hot wire touches the tube just right to find on an ohm check. And the only way to test the wire is to unhook the coils so you can test only the wire and hope it is touching so you can find it. When I find this problem or suspect it, I give up using the wire in the axle tube and run new wires outside it. Then you can pull the wire out of the tube and see the skinned insulation exposing it or close to it. There are a few ways to run the wire, but if you attach it to the tube, pick the back side so that the wire does not get beat up if you run over weeds or brush by accident. You can also run the wire attached to the bottom of the camper to cross over.
You are in the process of elimination at this point. All the checks above, except pulling the drums and the wire in the tube, are not that hard to do. Not sure if you are equipped to pull the drums; a sticky at the top of the towing forum will help show what you will be up against and how to do annual brake and bearing service.
Whenever I do a trailer brake or bearing maintenance pulling the brake drum, the odds are favorable that you might find a surprise inside. Nothing shocks me anymore about what one can find wrong inside; these brakes are not robust like the older auto drum brakes.
And while you have the camper up on jack stands of the block with the wheels off, assuming your camper has leaf springs, check the suspension; the nylon bushings that come standard in the spring eyes on many campers can be worn through between 8,000 to 10,000 miles on some or all of them. The equalizer center pin wears the fastest as the movement is more. When that bushing goes out, it starts wearing the casting; the whole equalizer starts to wobble and accelerates the shackle plates and pins wearing from spinning as the serrations on the heads of the pins are worn out. Another classic trailer failure is broken shackle plates from excess wear on the pins; once they start spinning due to the serrations being worn off that started from the wobbling equalizer, they start elongating a slot in the shackle plate which, in time, cracks the end of the plate off. Then the spring flies up into the fender well, leaving you stranded.
Hope this helps, and let us know how it goes.
John
Possible places that may create an actual short in the brake power line.
In the truck:
Check all wires from the controller to the 7-wire receptacle on the back of the truck. Blue is a color often used for the brake hot wire; confirm that it is your color in the harness and trace the harness from the controller to the actual pin in the 7-wire receptacle. If the insulation is skinned, it can touch the frame, which is a short to the controller.
On the trailer:
Is your 7-wire plug an add-on plug to the end of the cable, or is it all one molded cable and plug? If it is an add-on plug, it can be possible a strand of wire in the plug can touch another terminal from a bad wiring job. You can take them apart and check. If it is an all-molded cable and plug, this issue does not normally happen.
I'm not sure about your camper, but most newer campers have a junction box where the 7-wire cable enters and splits into camper DOT lights and the camper brake wiring. They have to connect to the camper blue brake wire in the 7-wire cable; that splice may have a problem.
Trace the camper blue brake wire out of the box all the way to the axle area, and look for skinned insulation.
Inside the brake itself (you must pull the drum to see inside), the magnet coil leads have small clips holding the wire to the magnet arm. Those clips have creaked or were not right from day 1, and the magnet wire gets skinned and can short to the ground. I have seen this; it is not common, but it does happen.
The coil comes loose from the magnet arm due to the clip breaking and gets ground up sideways over time. If the coil wires are exposed, that can be short. When this happens, the magnet is shot, and the magnet arm can also be bad. I have seen this too.
Then there is the worn insulation on the hot wire inside the axle tube. This is a classic failure mode. This is hard to test unless the hot wire touches the tube just right to find on an ohm check. And the only way to test the wire is to unhook the coils so you can test only the wire and hope it is touching so you can find it. When I find this problem or suspect it, I give up using the wire in the axle tube and run new wires outside it. Then you can pull the wire out of the tube and see the skinned insulation exposing it or close to it. There are a few ways to run the wire, but if you attach it to the tube, pick the back side so that the wire does not get beat up if you run over weeds or brush by accident. You can also run the wire attached to the bottom of the camper to cross over.
You are in the process of elimination at this point. All the checks above, except pulling the drums and the wire in the tube, are not that hard to do. Not sure if you are equipped to pull the drums; a sticky at the top of the towing forum will help show what you will be up against and how to do annual brake and bearing service.
Whenever I do a trailer brake or bearing maintenance pulling the brake drum, the odds are favorable that you might find a surprise inside. Nothing shocks me anymore about what one can find wrong inside; these brakes are not robust like the older auto drum brakes.
And while you have the camper up on jack stands of the block with the wheels off, assuming your camper has leaf springs, check the suspension; the nylon bushings that come standard in the spring eyes on many campers can be worn through between 8,000 to 10,000 miles on some or all of them. The equalizer center pin wears the fastest as the movement is more. When that bushing goes out, it starts wearing the casting; the whole equalizer starts to wobble and accelerates the shackle plates and pins wearing from spinning as the serrations on the heads of the pins are worn out. Another classic trailer failure is broken shackle plates from excess wear on the pins; once they start spinning due to the serrations being worn off that started from the wobbling equalizer, they start elongating a slot in the shackle plate which, in time, cracks the end of the plate off. Then the spring flies up into the fender well, leaving you stranded.
Hope this helps, and let us know how it goes.
John
