Fixing RV Trailer Brakes After Failure In Mountains

We love the mountains! We’ve been hiking, touring, seeing the incredible vistas – all during the beautiful autumn colors. The trouble with mountains is up and down, windy, curvy, steep, narrow roads. Not exactly the ideal driving for a large, heavy fifth-wheel trailer! When you are towing a heavy load, you really need to have good, reliable brakes…which we didn’t. We had a failure during our first 2 months on the road, so immediately set about fixing the RV trailer brakes.

RV Brake Issues

The problem had first shown itself after we first got the new rig, but had cleared up as soon as we stopped to investigate.  

Fifth wheels and most other heavy trailers have their own brake system that plugs into the back of the truck when hitched up. 

Our truck has its regular brakes, and also an engine brake or jake brake. The engine brake helps slow the truck down by downshifting the transmission and uses the turbocharger veins to create back pressure on the engine, which puts negative torque through the transmission. It also makes a loud roaring sound – you’ve probably heard it in semi-trucks when they stop.  

In the event of an RV trailer brake failure, we would still have the braking power of the engine brake and the truck brakes, but they would be much much slower and possibly ineffective if, say, you were careening down a steep mountain and a deer jumped out.   The brake issue we had on our trailer happened just a couple times before we left Michigan. We took time during our stay in Sugar Springs to remove all the wheels and check the brakes.

​How Electric Trailer Brakes Work

​Trailer brakes are composed of several parts. There are the brake drums, the brake pads, the brake magnets, and the wiring. The electrical current provided by the truck through the wiring energizes the brake magnet, which sticks to the brake drum and pulls the magnet back due to friction. As the magnet moves backward, it presses the brake pad into the drum on the outer rim and slows the rotation of the wheel.

Here is Tom showing how this works with our brakes:

Worn RV Trailer Brake Magnets

​When we removed the wheels to take a look at the brakes, we found that the magnets were pretty worn. We wondered if the magnets were so worn that the metal windings inside the magnets (that energizes it) were making contact with the metal drum and shorting the system out when it struck it just right.

We definitely knew one magnet was not working at all because the brake would not get hot after braking. It also could have been some frayed wiring which runs back to one side of the trailer then cross to the other wheels by passing through the axles. It could also be a loose connection on our connector to the truck, known as the pigtail. We planned to address all these possibilities (after all, our rig was ten years old).

We needed all new brake magnets, but couldn’t get the parts ordered, shipped, and delivered before having to move on to the next spot. Once we got to West Virginia and had 3 weeks in one place that we could go about fixing the RV trailer brakes properly.

Unfortunately, we lost our brakes on the mountains of West Virginia.

Luckily, it was on the interstate (didn’t have to stop at light or sign), traffic was light, and there was no need to stop suddenly. The mountains actually helped us in the fact that they slowed us down more as we went up the next incline.

​The warning on the brake control indicated an “Output Shorted”. This meant that something in the brake system was definitely shorting out again. The intermittent occurrence of this was troubling, and this one lasted the longest. Fortunately, we were only about an hour from our final destination for 3 weeks. When the brakes decided to work again, we drove nice and carefully the rest of the way.

Fixing The RV Trailer Brakes  

​Over a 3 day period, we replaced all the brake magnets, the wiring, and the pigtail. ​The wire in the axle turned out to be the major culprit: 

The wires had bounced around inside the axles and wore through the insulation, creating a short against the metal axle. The picture above shows one of the many frayed areas we found on the brake wires. No wonder we were shorting out! It’s amazing we had brakes at all.  

We rewired the brakes so that the wire is now on the outside and can be easily inspected. Yay, we had brakes again!

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