Many new trucks and SUVs have trailer brake controllers that help you stop a trailer with electric brakes. They’re great when you’re towing a trailer, but setting one up properly is key to making sure you don’t melt your trailer’s tires or go careening into the first ditch you see. There are a few guidelines for setting up a trailer brake controller but it’s easy to set one up and understand how they work.

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A trailer brake controller does what is in the name. But, it only works if you have a trailer with electric brakes and the right cables hooked up to your truck or SUV. And, the trailer’s electric brakes only work if the battery is charged, so make sure it has juice. A trailer brake controller is almost a necessity if you’re towing a big trailer, and especially if you ever need to back up a hill with a trailer.

Many trucks and SUVs come with integrated controllers, but you can find aftermarket controllers, too.

Start with a low number and work you way up, which is called “trailer gain.”  One way to set trailer gain is by setting the trailer brake controller to a low number, like 1 or 2, and then squeeze the brake controller manually toggles together. The toggles on controllers squeeze the brakes on the trailer manually.

Start your truck and take your foot off the brake. Squeeze the controller. If the truck starts moving in gear, the trailer brakes aren’t working. Manufacturers recommend that you set the controller at a small number like 1 or 2, and then drive to 25 mph or so, and squeeze the brake controller. If it locks the wheels, the number is too high. So, if you set it at 3, squeeze the buttons while driving slowly, and hear a squeal, the controller is set too high: lower the number and try again. Your owner’s manual will have specific instructions for your vehicle.

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The controller connects to your truck or SUV’s braking system. When you hit the brake pedal, the trailer hits its brakes. But, since not all trailers weigh the same and since some have two wheels, others have four, and tires come in a variety of sizes the pressure you need to apply varies. That’s why there are several settings on a controller.

If you are towing a trailer, and it is hooked up to your truck or SUV, then yes, leave it on. When you don’t have a trailer connected, it doesn’t matter if it’s on or off. If the battery dies, or the trailer becomes unhooked, the breakaway switch will trigger and the trailer should automatically stop.

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It’s hard to tell just by pressing the brake pedal if your controller is working. Instead, drive slowly and squeeze the buttons on your brake controller and you should feel your trailer slow you down. If you don’t, you may need to set your gain properly or you may have a faulty system. Most likely, the battery for the electric brakes is dead, so make sure that’s charged before you test the trailer brakes. Also, it’s always a good idea to make sure the brake pads and tires in the trailer are in good shape.

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