Most trucks, vans, SUVs and RVs made since the mid-1990s are set up to use an electronic trailer brake controller. These vehicles include a factory-installed “quick plug” under the dash that connects with a standard brake controller. Many pickup trucks made in the last 5 years even include a brake controller built in to the dashboard, and absolutely no installation is required.
But even if you have to splice into your vehicle’s wiring to install a brake controller, the process is not as difficult as you might think. Brake controllers work on very simple principles, and once you understand what they do and how to use them, you’ll be very glad to have one.
About Trailer Brakes
Most recreational trailers use electric brakes. The exceptions are generally rental car-hauling trailers, which use “surge” brakes and some large fifth wheels, which use air brakes. You can buy travel trailers and car haulers with surge brakes, but they are less common than electric. All types of trailer brakes generally use drum brakes, but some are starting to use discs as well. The differences between brake designs are significant.
Surge brakes are hydraulic, and use the trailer’s natural momentum to actuate the brakes. When you step on the brake in your tow vehicle and slow down, the trailer pushes against the hitch and presses a hydraulic cylinder. The more you slow down the vehicle, the more pressure on the trailer brakes. When they are adjusted properly, surge brakes are smooth and easy to work with. The downside is that you cannot separately actuate the trailer brakes if the trailer is swaying.
Air brakes use compressed air to actuate the brakes, and they require extensive additions to the tow vehicle, including compressors and valves to control the air pressure and flow. Since these are quite rare in recreational towing, air brakes are not covered in this series.
Electric brakes are more simple than surge brakes, but they require a brake controller in the cabin of the tow vehicle. Electric brakes use electromagnets to actuate the drum brakes, and you control the electricity to the brakes with the brake controller and the brake light circuit on your vehicle. Electric brakes work very well when adjusted properly, and you can also reach over with your hand and use the brake controller to apply a small amount of braking force if the trailer begins swaying. That’s handy when descending hills, in high winds, and when you’re being passed by large 18-wheelers.
About Trailer Brake Controllers
Trailer brake controllers are small boxes that generally have just a few controls. There may be sliders or wheels for sensitivity and gain, and there’s almost always a slider to allow you to activate the trailer brakes without stepping on the tow vehicle brakes.
Figure 7-1: Trailer brake controller
The Sensitivity adjustment may be automatic or it may be manual. This adjustment allows the brake controller to activate the trailer brakes any time it senses your tow vehicle slowing down. This prevents your trailer from pushing too hard against the hitch and jackknifing.
The output (gain) adjustment simply modulates the amount of electricity sent to the brakes. This adjusts the amount of braking force applied. Heavier loads require more gain to generate more braking force, but if you use too much gain, you’ll lock up your trailer tires every time you step on the brakes.
The activation slider (or manual control lever) delivers some electricity to the brakes, and you use it when setting up the controller of if the trailer begins to sway. Applying just a bit of trailer brake is generally enough to stop the sway and pull the trailer back in solidly behind your vehicle.
Wiring for Trailer Brakes
If your truck, van, RV, or SUV was made after the mid-90s and if it came from the factory with a Class III or better towing hitch installed, chances are that it also has a quick plug under the dash for a brake controller. A “pigtail” connector might also have been included in the glovebox. If that’s the case, you simply need to use the standard plug or use the pigtail connector to wire into the vehicle plug, then mount your brake controller somewhere on your dashboard. Generally, controllers are installed near the driver’s right or left knee.
Figure 7-2: Some of the styles of brake connector quick plug to fit different vehicles
If your vehicle is not prepared with a quick plug, you’ll need to tap into your brake light wiring. Find the brake light switch – it may be mechanical and attached to the pedal, or it may be hydraulic and somewhere in the engine bay. Wherever it is, you’ll need to run a 12 volt power wire, a ground wire, and a brake light wire to the controller, and then a wire from the controller back to your vehicle’s trailer wiring connector.
Wiring in a brake controller is generally too complicated and important a job for an amateur. If you’re confident of your skills, you can do it, but it’s generally better to take this job to a professional if you haven’t done it before.
Finally, if you’re lucky enough to have a brand new truck with a brake controller installed in your dash by the factory, you’re all set and your controller should work with all standard electric trailer brakes.
About Breakaway Brakes
Many larger trailers are required by law to use a breakaway system with the brakes. This safety device protects you and people around you in the worst case scenario. If your trailer comes loose from your vehicle, it’s an unpredictable and highly dangerous situation.
Figure 7-4: Breakaway battery
A breakaway brake is simply a small battery on your trailer and a switch connected to a strong cable. You attach the cable to your vehicle’s trailer hitch and if your trailer comes loose and your safety chains fail, the trailer will pull the cable as it breaks free of your vehicle. The switch will activate the battery and apply the trailer brakes strongly.
Figure 7-5: Breakaway switch and cable
If your trailer has a breakaway system, maintenance is simple. Check the breakaway battery regularly to make sure it is charged, (most high quality systems include a charger) and check the breakaway cable to make sure it’s in good condition. Always connect the breakaway cable to your vehicle securely. You can test the breakaway system by pulling the cable. Your trailer brakes should immediately activate and lock up the tires. To disengage the breakaway, simply replace the breakaway cable in the switch.
Trailer Brake Service
Like any other brakes, trailer brakes require regular service. The heavier the loads you tow, the more frequently you should inspect and adjust your trailer brakes. Every 6 months is a good interval for most recreational trailers.
Because your trailer brakes are almost always drum brakes, you generally have to use a flat screwdriver or brake adjustment tool to perform the adjustment. Follow the directions in your trailer’s brake handbook (it’s usually a separate document), but most brakes use a “star wheel” adjuster and have you tighten the brakes until the wheel does not turn, then back off a given number of “clicks” until the wheel turns freely. Over time, you may need to replace the electromagnets as well, or replace the brake shoes and drums, but most trailer brakes are gently used and will last a long time.
If you’re not confident of your ability to inspect and adjust your brakes properly, take it to a professional trailer shop. They’ll have you in and out quickly and it doesn’t cost much to have this work done.
If you have the trailer shop adjust your brakes, have them lubricate and tighten your wheel bearings and inspect your tires and valve stems at the same time.