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Trailer Brake Controller Wire Testing

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How to Test Wiring on a Brake Controller for a Trailer

Today we are going to cover a few notes on testing an electronic brake controller. What we are going to cover here is going to apply to virtually all brake controllers. Basically, if you run into a problem where you think your brake controller is not working, well, it could be a the brake controller or it could be something in the truck itself, in the connector or c it actually could be problems in the trailer. What we are going to show you today is how to look for problems that will either rule out the brake controller or make sure that it is the brake controllers fault. Just like any electronic devices, they seem to have a limited lifespan some will work for years and some will not. But this way you can also verify that it is working good.

All right, the steps involved to test a brake controller are going to be pretty easy. You need one definite tool you need a light tester, like we have one here. Basically you ground it onto the body of the vehicle and you use this to probe the wire you are going to test. And it is best to use an incandescent bulb because a lot of times voltmeters do not put out sufficient load to actually activate the brake controller itself, because brake controllers are activated by the magnets that are on the trailer, and thus a load. So you can replace that load with a simple incandescent light bulb. So one of the first things you want to check if you suspect your brake controller is pretty simple. Go ahead and make sure you have power going to the brake controller.

So we will our ground our tester, and the black wire is going to be positive so we will go ahead and test it. Okay, we know we have got power going in, so that means you have a good 12 volts going into it. The next thing you want to double-check is the red wire. That is typically the signal that is coming off the brake switch. Again, the same thing applies. So go ahead and put your tester on that and then hit your brake switch. And if you have got signal going to it, then that part of the circuit is fine, too. If you do not have power going, then obviously your brake controller is not going to work when you hit your foot brake. Now the last thing you want to do is go ahead and test the blue wire. Now the trick is, with this, you want to go ahead and disconnect this blue wire from the rest of the vehicle. The reason for that is that it eliminates any problems with the connector on the back of the vehicle or the trailer itself. That way you verify you have output coming from the brake controller itself. So you test that, and then press the manual override. And then if you have a time delay brake controller you can do the same thing with the foot brake, kind of an additional little test you can do.

If all that is working, then your brake controller is fine, and there is something else usually down the road from that. So basically the next you want to check is to make sure your blue wire is connected to the harness securely, and then go out to the back of the truck to the rear connector of the truck. Again you probably want to have somebody manually activate the brake controller and make sure you have current from the blue wire out the end of your connector out back. Now if that is all fine, then you know there is something definitely wrong with your trailer, and you have to start troubleshooting from there.