Electric brakes

[TayzGpa]

I hope I can explain this with some level of clarity.

I have a "new-to-me" 2016 Montana 3711FL.
A couple of weeks ago, I had a blowout on one of the rear tires.
When the tire blew, it cut the brake wires on the wheel in front of it.
I have replaced all 4 tires with new ones and while I had all 4 wheels off I pulled the brake drum off of the "wire damaged" front wheel and reconnected the wires using a couple of wire unions.

I wanted to make sure that the brakes worked after reconnecting the wires on the wire damaged wheel. So... while I had the trailer jacked up I connected the 5th wheel electric cable to the truck bed connector in my 2012 Ford F350. Started the truck and while I spun the wheels, my wife would apply the break pedal.

I did two brake tests to make sure they worked and here is what I found.

First test used the brake pedal in the truck.
While applying the break pedal, only the rear wheel on the opposite side of the trailer (opposite of the blowout wheel) would stop. I could here the blowout wheel hum but it never engaged fully. Neither of the front wheels engaged.

Second test did not use the brake pedal but used the manual "slider" switch in the truck cab.
When the "slider" switch was applied, both rear wheels would stop and one of the front wheels. The "wire damaged" wheel never stopped.

I don't have a clue how these electrical brake systems work. Is it normal for only the rear wheels to engage when the brake pedal is applied or is something else going on.

Any info would be appreciated.
Thanks in advance.

[tspoon]

All 4 are hooked up together. You may have to adjust each brake. If you go to lippert web site, they will tell you how.

[rohrmann]

You should have self adjusting brakes on that rig. You need to check all the splices in the brake wiring, not just what you found broken. It is also possible that a wire has pulled apart inside the insulation, where it appears to be intact, but the actual copper wire is broken.

[GAinaMontana]

Maybe I can help with some of your questions. First, your f350senses that it is moving at less than 12 mph and is reducing the voltage to your electric brakes that would sent at higher speeds based on truck brake pedal pressure. That is the reason you see more trailer braking with the slider.
I'm guessing on this one but maybe you reversed the polarity on the brake that doesn't respond at all.
For future consideration, consider dumping the electric brakes for discs and a set of Sailums.
Hope this helps. This is a great place to get help.

[TayzGpa]

Originally Posted by rohrmann

You should have self adjusting brakes on that rig. You need to check all the splices in the brake wiring, not just what you found broken. It is also possible that a wire has pulled apart inside the insulation, where it appears to be intact, but the actual copper wire is broken.

Thank you, I will check that. Is it possible/easy to ohm that wire out to see if it is broken internally?

[TayzGpa]

Originally Posted by GAinaMontana

Maybe I can help with some of your questions. First, your f350senses that it is moving at less than 12 mph and is reducing the voltage to your electric brakes that would sent at higher speeds based on truck brake pedal pressure. That is the reason you see more trailer braking with the slider.
I'm guessing on this one but maybe you reversed the polarity on the brake that doesn't respond at all.
For future consideration, consider dumping the electric brakes for discs and a set of Sailums.
Hope this helps. This is a great place to get help.

You know, I wondered about that speed thing. I guess that would explain why the one wheel only hummed. Yes, I also thought that perhaps the wires might be reversed so I swapped them. Still nothing. Thanks for the info about the voltage/speed relation.

[jimandjuliet]

brake wires not polarity sensitive

[GAinaMontana]

When you pulled the damaged brake drum were the inside surfaces bright and shiny.? That would tell you if the brakes were previously working.

[WeBeFulltime]

Originally Posted by GAinaMontana

Maybe I can help with some of your questions. First, your f350senses that it is moving at less than 12 mph and is reducing the voltage to your electric brakes that would sent at higher speeds based on truck brake pedal pressure. That is the reason you see more trailer braking with the slider.
I'm guessing on this one but maybe you reversed the polarity on the brake that doesn't respond at all.
For future consideration, consider dumping the electric brakes for discs and a set of Sailums.
Hope this helps. This is a great place to get help.

[psomers]

If I have a wheel in the air and just want to check trailer brake wiring, I pull the break away cable. The wheel should lock up. You will be able to rock the wheel back and fort maybe 20* but not rotate it. To reset break away cable just push it in.

[mtlakejim]

Every RV owner should have a volt ohm meter and learn how to use it! A VOM will allow you to verify good voltage back to your brakes and that will answer a lot of questions right off the bat.

[mlh]

Originally Posted by psomers

If I have a wheel in the air and just want to check trailer brake wiring, I pull the break away cable. The wheel should lock up. You will be able to rock the wheel back and fort maybe 20* but not rotate it. To reset break away cable just push it in.

I agree with this. If one still isn’t working take the wheel and hub off. Then pull the plug again and with a piece or metal check the magnet to see if it’s working.
Lynwood

[TayzGpa]

Ok, I think I might have figured it out.

Looking under the trailer on the street side (drivers side)

Above the REAR wheel there is a slit in the underbelly which has 2 wires coming out of it that run to the break wires on the rear wheel.

Above the FRONT wheel there is a slit in the underbelly but there are no wires that come out of it. I suspect that these 2 wire may have been torn out when the brake wires were cut on the front wheel when the tire blew.

I traced the brake wires from the REAR wheel up through the slit in the underbelly and found that they attach to a blue wire and a white wire via wire nuts. I traced the blue and white wire further and found that they ran to 2 wire nuts next to the slit above the FRONT wheel. From there the blue and white wire run towards the front of the trailer and into oblivion somewhere.

I suspect that if I run 2 wires from the wire nuts above the FRONT wheel down to the front brake wires that it will fix the front wheel brakes not working.

Thoughts?

[dieselguy]

The two wires coming out the backing plate on your front brake have to connect to the main brake wiring that you have found. Like mentioned, there is no polarity as to the magnet wires ... either way will work. I like to put heat shrink on the connections or use liquid electrical tape to help keep the water out.

[Ishler]

The blue wire is the feed from the umbilical cord junction box, white is the ground/return.