Checking Electric Trailer Brakes and Brake Controller for Proper Function

Question:

Just installed 4 new electric brake assemblies I purchased from etrailer. When either the manual lever is fully engaged or vehicle brakes are pressed I get minimal brake action...I can still turn tire by hand. I do have the brakes adjusted so there is a bit of drag without brakes engaged. I did some voltage testing but was a little confused about the results. The controller is getting 12v. Red wire is producing 12v when brakes pressed. The blue wire I wasnt 100 sure if I was testing correctly so I did it a couple ways. 1 I cut the wire and when I put my meter leads on both sides of the cut wire I got a constant 12v regardless of whether or not the manual lever was pressed I had the gain turned all the way up. 2 Put meter leads on white and the cut blue controller side...no power. Controller light was also off so that seems to make sense 3 Reconnected blue wire. Put leads on blue and white. Voltage would go up and down with the manual lever to a max of 11.7v Tested wires on trailer side at tongue. Getting 12.1v from hot. Cut blue wire and put leads on either side...got constant 12v regardless of brakes being activated. Lastly, I put one lead on blue and one on ground and would get a max of 8v when either manual lever or brakes fully engaged max gain. Does this seem to indicate a bad controller? FYI, trailer hasnt been used for 18 months or thereabouts. Controller was working at that time but I have no idea if it was working when I changed brake assemblies. Controller is 13 years old.

asked by: Gregg A

Expert Reply:

From the testing that you have already done, it does sound like it's a bad controller. But you can verify a few things first.

If you have power going to the brake controller (black wire), and you are getting a signal only when the brake pedal is pressed on the red wire, that part is functioning properly. You should get a signal from the blue wire when you press the brake pedal or hit the manual override lever. I recommend testing close to the controller rather than at the back of the trailer connector. This way you can verify that the controller is sending the signal back.

I would also check the back of your vehicle's trailer connector for corrosion or any damaged wires. If you verify that the controller is sending the signals, the next place to check is at the trailer connector. If there is corrosion it may not let all the power to be sent to the trailer, or cause a short.

If you have another vehicle that has a brake controller I would recommend using that for testing the trailer, so you can isolate each item. If the trailer works fine with another vehicle, it's more than likely an issue with the controller or connector. But if the

You can also check the brake assembly magnets. I'll link an article that explains the process of testing the brake magnets. I don't think that they are the cause, but it doesn't hurt to check.

If you are looking to replace the controller I really like Tekonsha Prodigy P3 Trailer Brake Controller # 90195. It's proportional rather than time delayed, so it applies the brakes on the trailer at the same time and intensity as your tow vehicle. So there's a nice smooth reliable braking.

I linked all the brake controller, and a few help articles for you to check out.