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Electric Trailer Brakes not Working  

Question:

I can not make brakes work on a trailer I hove electric brakes using 7 wires

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Expert Reply:

There are a number of reasons why the brakes on your trailer may not be working. Lets start with the easiest things to check.

First, check the vehicle and trailer connectors for corrosion. This can cause a short inside the connector and the brake feed circuit and ground are at the bottom of the connector so moisture affects these connections first.

Next, check the ground wire on the vehicle and trailer connectors, trailer brake magnets and the brake controller itself. If there is a bad ground connection the trailer brakes will not work.

Next, check the brake controller wiring. Sever the blue brake output wire, leaving enough room to splice it back together when testing is done and then apply the manual slide. Using a circuit tester, like item # 3808, you should get output to the trailer brakes, blue wire. If the manual slide activates the trailer brake output wire properly, try the brake pedal. If the brake pedal activates the brake output properly the problem is farther back either in the vehicle wiring or on the trailer.

If either the brake pedal or the manual slide are not functioning properly you will need to test the wires going into the brake controller. Make sure you have power entering the brake controller on the black wire and on the red wire only when the brake pedal is pressed. If these wires test correct, and there is no output, your brake controller most likely needs to be replaced.

Finally, if those troubleshooting measures do not locate the problem, you will need to check the trailer brakes and brake magnets themselves. We have an article detailing how to test trailer brake magnets properly with a multi-meter, like part # PT89ZR, and we have a video showing the proper installation and adjustment of trailer brakes, see links.

expert reply by:
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Bob G
Leo L. profile picture

Leo L.

3/17/2020

I have power on all four magnets but changing the gain doesnt seem to have any affect on break strength.

ChrisR profile picture
Etrailer Expert

Chris R.

3/17/2020

If you're getting appropriate power on the brake magnets, I wonder if the assemblies themselves just need to be adjusted. You can use something simple like a flat head screwdriver to turn the starwheel at the bottom of the brake assembly. Just adjust until there's a slight but constant drag of the shoe pads on the drum. You can also skip ahead to the 4:40 mark on the video linked below to see this in action. Let me know if this doesn't help and we can go from there.
BruceM profile picture

Bruce M.

2/25/2021

@ChrisR Hi Chris, I have a 2007 Dodge Ram 3500 with a Draw-tite activator 2 brake controller, I’m having issues with my trailer brakes not activating (atleast I think so). The reason I think it’s not working is my brake controller is not showing the braking speed while braking. I just got the trailer junction box and pigtail rewired because the brake controller was displaying Overload. What do you think is wrong?
JonG profile picture
Etrailer Expert

Jon G.

2/26/2021

@BruceM Check to see if your brakes are humming when you use the manual override for your controller. You should hear a low hum or buzzing noise at each assembly during testing. If you don't hear any noise at all then you either have a miswired controller or it needs replacing. To check your wiring you need to use a circuit tester and test the 4 wires on the pigtail from the brake controller. The following colored wires should be connected to the following circuits. Blue - 7-Way Output to Trailer Black - 12V Power White - Ground Red - COLD Side of Stop Light Switch (only gets hot when brake pedal is pressed)
See All (5) Replies to Leo L. ∨
Leo L. profile picture

Leo L.

3/20/2020

Hi,After doing some further checks with the sliding bar it seems that with an mt trailer the gain had to be below 4 before the wheels stopped locking and showed appropriate drag. Probable somewhat due to the fact that drums and backing plates are new.Thx for the help.

ChrisR profile picture
Etrailer Expert

Chris R.

3/22/2020

Got it! I'm glad you were able to get everything sorted out. Please just let me know if anything else comes up.
Derrick F. profile picture

Derrick F.

3/24/2020

I recently did the trailer brake install on one axle and I noticed the smell of brakes from my driver side and some excessive heat while the passenger side has no heat at all. I connected the electrical wires and all.

ChrisR profile picture
Etrailer Expert

Chris R.

3/24/2020

It's possible that the driver's side assemblies just need to be adjusted a bit. It sounds like they are dragging too much, which is causing the smell and heat. Take a look at the video linked below and skip ahead to the 4:50 mark to see this process. It's also possible that the driver's side brakes are hot because they are doing all the work. Make sure the passenger side assemblies are properly grounded to the frame and the brake input wires are securely connected.
Ken L. profile picture

Ken L.

5/12/2020

I recently bought a 16’ trailer. When trying to put new lights and wiring I discovered that the trailer has brakes. The drivers side has a wire going to the back side of the brakes. No wire on passenger side wheel. Trailer came with lights and a 4 prong blade without the brake wiring. Opened the drivers side and everything was there. Very clean and about 50% left on pads. Stripped the wires and connected to a jump box- no movement in brake. Do I run the wiring for brakes and then fix brakes or proceed a different way?

ChrisR profile picture
Etrailer Expert

Chris R.

5/15/2020

I would go ahead and replace the brake assemblies first, and then re-do the wiring once they're in place (otherwise you'd be wiring them up twice). I linked an article below on adding electric brakes that you might also find helpful.
Anthony profile picture

Anthony

6/21/2020

Replaced brakes have power to vehicle and trailer but not when connected

ChrisR profile picture
Etrailer Expert

Chris R.

6/24/2020

Can you tell me how you're testing the brakes when the trailer is attached?

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