An RVer asks: “I have a question about brake controllers and travel trailers. How do you adjust them? How do you know if they are too tight or not adjusted correctly?” These are great questions, and we can offer some suggestions.
A Little Brake Controller Theory
Travel trailers and fifth-wheels are typically equipped with electric brakes. When you step on the brake in the tow vehicle, electric current is sent from the tow vehicle back to the trailer. This current runs to each wheel assembly, then through an electromagnet. Energized, the electromagnet forces the trailer brake pads to press onto the trailer’s brake drums. The friction between the brake pads and the drums slows the vehicle—and converts kinetic energy (for our purposes, the energy moving the trailer) into heat.
The job of the brake controller is to send the appropriate amount of current flow back to the brakes. You could send a full jolt of electricity back to the brakes, and they’d respond by jamming the brake pads into the drums, locking up the brakes. That’s converting that kinetic energy into heat way too fast—skidding the tires, making vehicle control difficult or impossible, and wearing out the brakes in a hurry.
Set properly, the brake controller also pairs up the tow vehicle and the trailer in the sense that both are braking for themselves. Too little power to the trailer brakes, and slowing or stopping the trailer falls to the tow vehicle’s brake system. Too much power to the trailer brakes, then the trailer brakes get the job of slowing or stopping the tow vehicle. If the controller is not set properly, you’ll be needlessly wearing out the brake system of one or the other, and that’s a costly and unsafe proposition for sure.
Why Adjust Your Brake Controller Settings
It’s important to set the brake controller settings for the job at hand. For some, this will mean doing the initial setting, and tweaking the system to get everything honed to “towing perfection.” However, if you use your tow vehicle to tow different trailers—for example, using your pickup to haul your travel trailer, and then on other occasions using it to haul a utility trailer—, the different trailer weights will require adjusting the controller more often. Horse trailer users find this a frequent issue—hauling maybe two horses today, one tomorrow, or deadheading with no load on at all.
Different brake controllers require different approaches to settings. That’s why it’s critical that you know what brake controller you have installed in your tow vehicle, and you have the manufacturer’s instructions on setup. Don’t have the instruction manual or quick setup guide? Get the manufacturer name and model number, hit the Internet, and look for it. If your controller is old enough not to have a presence on the Web, then it’s high time you got a new brake controller.
A Real Life Example
We’ll walk through an example with one popular model, Tekonsha’s Prodigy P2 controller. A snowbird friend of ours was preparing to leave the Southwest to beat the heat by heading to Wyoming, and she was concerned that her brake controller needed adjusting—she had changed fifth-wheels since her last adjustment. We obliged, and one of us jumped in her rig with a spotter along.
Tekonsha recommends setting the power setting for its unit at “6” for a starting point. This means that with the trailer attached and the engine running, the operator pulls the manual override lever on the controller all the way to the left—maximum brake. While holding the lever, you then adjust the power control knob until the digital setting shows a 6 on the display. We did that easily enough—and at the same time, we also turned off the “boost” setting on the control.
From there, you locate a flat stretch of pavement (not gravel), bring your speed up to about 25 miles per hour, and pull that manual override lever on full—don’t step on the tow rig’s service brakes, simply yank the controller’s lever. If the brakes on the trailer lock up, stop, pull the override lever on full, and reduce the power level down a notch. Do this until the brakes no longer lock up. On the other hand, if the trailer doesn’t respond with a lock up, you’ll up the power a notch. Repeat this process until you hit lock up, and then back it off slightly, and your power level is set.
In our case, we dialed all the way up to the maximum level and never got any notion at all that the trailer brakes were doing anything. Next day, an inspection revealed that the trailer brakes had to be manually adjusted out—the lining was worn down enough that the brakes weren’t making contact with the drums. That can happen—the vast majority of trailer brakes, unlike those on cars and trucks, are NOT self-adjusting. They need to be adjusted “out” as lining wears down.
With the adjustment done, we made another controller adjustment run. Again, we started at level 6, and worked our way up—almost all the way to the top of the scale. We never could get the brakes to lock up, but the trailer brakes definitely did their job. Why couldn’t we lock them? Very heavy loads can be more than the system allows for a lock up. Her 40-foot (and probably overloaded) trailer just couldn’t be locked up. We recommended she run the trailer across a scale, and begin the job of tossing out excess baggage.
Other Brake Controller Considerations
Regardless of your brake controller make and model, there are some observations that apply across the board. Brake temperature can make a big difference. It’s not unwise to pre-warm your brakes prior to dialing in the right setting. Your manual will tell you how to do that. Then it gets dicey—in our case, the manual advises to engage the manual brake lever on the controller while cruising down the road “at 25 miles per hour or less.” By the use of the manual engagement lever on the controller, you’ll be using the brakes on the trailer, not the tow vehicle. All very well and good, but if too much power is routed back to the trailer brakes and you’re cruising along at 25 miles per hour, you may have a BIG mess to clean up back in the trailer should the brakes lock up. At least one expert recommends checking your brakes in your driveway at say, 5 miles per hour. The objective is to see to it that the power setting of the controller will slow the rig down—NOT lock the brakes.
Here’s some other advice you may not find in the manual. Doing an initial test in a gravel lot may give a lot more feedback than on pavement—you’ll hear that gravel if you lock up, and the skid marks are a clear indicator that you’ll need to back off the gain adjustment on the controller. Once we know where things sit on gravel, then fine-tuning on pavement ensures we’ve got the controller set where it needs to be.
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The trailer brakes not locking up the trailer’s tires – even at maximum setting – does not necessarily mean that the trailer is overloaded (even if the trailer in the example was overloaded). It may simply have more tire traction than braking capability, which is okay. the mass of the tow vehicle affects the braking level for lockup, but not the appropriate controller setting, so the method is fundamentally flawed. The “set for lockup” method is routinely recommended by manufacturers of brake controllers, but often does not result in the right controller gain setting.
What do you figure if the trailer brakes lock up and reverse lights on tow unit come on when the trailer plug is simply connected to the tow vehicle?
Any opinions on this is appreciated.
Russ DeMaris says
What you want to do is first check to make sure the orientation of the trailer plug into the tow vehicle receptacle is correct. The “key” should fit in the slot of the tow vehicle port. If that’s OK, then you’ll need to check the wiring. Easiest to start with that coming from the tow vehicle. You’ll need a diagram of the receptacle wiring, based on the number of contacts in it. Use a test lamp, clipping the negative clip to a known good ground on the vehicle, then going around each contact and ensuring that when say, the right turn signal is on, the correct contact gives you a blink, backup lamps when in reverse, etc. If the tow vehicle end proves good, then the problem is in the wiring of the trailer.
Hope this helps.
Russ. Thanks for the response.
The truck trailer plug socket is deffo the issue.
I have had my rig pulled by a few other trucks without issue.
On top of that I’ve found a stray wire at the rear of the connection from wired to back of how vehicle plug that’s touching other terminals. The actual blades that the trailer end meets On truck end are not even attached to the socket and can be spun in the housing now which means the proper mating of plug to socket can be horribly wrong.
On top of THAT, the truck owner just told me that this has happened previously with another trailer.
Clearly I need to rewire the entire thing.
Now my question is this. The 12 volt power on the tow vehicle socket gets wired via a relay which sends power only with key in on or run position correct?
Power comes from the battery of the how vehicle through the relay and to the proper terminal on the socket correct?
The 12 volt on the trailer plug goes from plug wire to 30 amp self resetting circuit breaker and then to battery correct?
Thanks for the help.
Gregory Suelzle says
At my well established horse trailer shop in Horsetown USA Norco, I was advised by the absolute expert to adjust them by taking your foot of the brake and then letting yourself creep forward about 20 feet then triggering manual brake controller fully. If it is set right you will slowly stop like a normal smooth stop in busy town traffic. If you don’t feel the brakes immediately then you can brake with your foot and adjust thegain up. Some trailers will not activate brakes at slower speeds so this may not work if that is the case. Using this method is very easy to perform, and does not involve locking up the brakes. You don’t have to work about someone rear ending you, because you are slowing down in a very normal fashion. Since this is very easy and low risk one can do this more often. One can also feel the amount of braking you are getting and it is much easier to adjust. With this method you don’t get too much of trailer braking which is to be desired.
Sariah Meagle says
My dad is planning across the country in his RV but the brakes are off. It was explained here that it’s important to have the brakes adjusted before a long trip. Moreover, it’s advisable to consult professionals when dealing with RV brake repair services.
Natalie Roberts says
When I step on the brakes, my tires will start screeching.
I thought it was broken. But your post has given me a lot of useful information. Thanhs very much !
Asst Prepper says
Gregory Suelzle has the right idea