Electric trailer brakes, plug 'em in, they lock up....

[montejw]

Sort of OT, but sort of not. My wife just bought a horse trailer with electric brakes. Her old trailer has electric brakes, and they work. When we plug in the "new" trailer the brakes lock up. Also, the indicator light on the controller doesn't light up at all with the new trailer plugged in, but works with the old trailer plugged in. She's hauling 4-5 horses, so the brakes matter.

The controller doesn't like something in the new trailer, got any tips on what to look for? There's only one wire going to the brakes isn't there? When I test the pin on the truck recepticle it's hot, 12 volts with nothing plugged in. Plug in the new trailer, the wheels are locked up and no indicator light on the controller. Plug in the old trailer and the brakes are controlled by the controller and the indicator light works, goes from green to red as I push the brake pedal.

I mow her pasteur with our NH TC30, now we're on topic

 

[wushaw]

Sounds like the trailer brakes are doing what they are suppose to.
Your not suppose to have voltage on the truck side when the brakes are not applied.

 

[Diamondpilot]

There are two ways manufactures wire trailer brakes. They swap two pins. I run into this all the time due to towing over 100 different trailer each year. There are only two ways to wire them as a standard. My suggestion is to look the plug on the other trailer and match it to the old trailer that works. GM trucks will also lock up some trailers with no controller installed in the truck.


Here is a good site to help
Marksrv.com 7 way wiring diagram page
Chris

 

[montejw]

Sounds like the trailer brakes are doing what they are suppose to.
Your not suppose to have voltage on the truck side when the brakes are not applied.

So maybe the pin I think is e-brakes is aux power? The old trailer does have interior lights and such. Guess I'll look at it assuming that's what's going on.

 

[montejw]

There are two ways manufactures wire trailer brakes. They swap two pins. I run into this all the time due to towing over 100 different trailer each year. There are only two ways to wire them as a standard. My suggestion is to look the plug on the other trailer and match it to the old trailer that works. GM trucks will also lock up some trailers with no controller installed in the truck.


Here is a good site to help
Marksrv.com 7 way wiring diagram page
Chris

If you look at that page #2 Blue is HOT, 12 volts on the truck. When you say there might be 2 pins swapped, might they be #2 and #4?

 

[montejw]

There are two ways manufactures wire trailer brakes. They swap two pins. I run into this all the time due to towing over 100 different trailer each year. There are only two ways to wire them as a standard. My suggestion is to look the plug on the other trailer and match it to the old trailer that works. GM trucks will also lock up some trailers with no controller installed in the truck.


Here is a good site to help
Marksrv.com 7 way wiring diagram page
Chris

Update: I just tested the truck recepticle and both #2 and #4 (according to the page linked above) are hot. I guess the next thing to do is figure out how the old trailer is wired, which wire goes to the brakes.

 

[Birdhunter1]

I ran into this once on a 7 pin to 6 pin adapater. I got the adapterat a trailer supply house and the guy said if your brakes are locked up pull this apart and switch these two wires. I don't remember what the colors were but I remembered I had to switch them in the adapter.

 

[montejw]

I ran into this once on a 7 pin to 6 pin adapater. I got the adapterat a trailer supply house and the guy said if your brakes are locked up pull this apart and switch these two wires. I don't remember what the colors were but I remembered I had to switch them in the adapter.

Hmmm, the new trailer does have an adapter like you mentioned. I'll look at that too, thanks.

Just took the adapter apart, what's it going to take to jog your memory on the wires to swap??

 

[Diamondpilot]

He is right about swapping the adapter. So what you are saying is you have a 7 pin on the truck and a 6 pin on the trailer. You are using a adapter between the two????


Chris

 

[Diamondpilot]

Ok, did some thinking. I have only ever used on of these and after that I started cutting off the old style 6 pin plugs and putting on the new standard 7 pins.

Anyway after trying to remember its probably the adapter. Your center pin can be 12volt or brakes. You can swap them. What it sounds like to me is that that seems to be the problem and why your brakes are locking up, 12volts going strait to them.

Chris