Trailer Brakes Locked Up

[MotorCityBear]

First post and I need some advice.

I just bought a used trailer off of craigslist. The trailer (16x6.5) is in great shape and has electric brakes.

When I bought it, as soon as I plugged (round 7 pin connector)it into my 2019 Chevy Colorado, (with the trailer tow package and integrated trailer brake controller) I got a service trailer brake system message on my dash and the trailer brakes were locked up.

I unplugged the trailer, plugged it into the Seller’s F-150 and everything was OK.

So I took my truck into the Chevy dealer thinking the trailer brake controller module was bad but they said there is no problem with my truck.

The Seller then brought the trailer to my house with no issue.

So my question is, where do I start trying to diagnose this problem.

I thought trailer wiring was basically the same on all vehicles, trailers, but could the trailer be wired differently?

Any advice would be much appreciated.

Thanks for reading this far!

 

[4570Man]

I guess the possibility exists that the seller has wired his truck wrong and then wired the plug wrong to match his truck but I’m guessing it’s an issue with your truck wiring.

 

[WM75Guy]

If he wired in an aftermarket brake controller he may not have used the standard wiring configuration. He may have swapped wires on the trailer to make it work. I would start by opening up the trailer plug. Here is the standard wiring schematic.





I bought one of these wiring checkers for less than $20 at O'Reillys. Well worth it to let me know if the truck is the problem or the trailer. Much easier than a test light, which is also handy to have.

 

[Roadworthy]

Start with how many pins are on the trailer connector. I think seven is standard now but with the six pin connector there were two different "standard" configurations. If your truck has the current standard seven pin connector and the trailer does as well the trailer needs wired to match the truck. Look especially at the brake controller pin and the auxiliary power pin. Sometimes these are swapped and if they are you are locking the brakes whenever you connect the trailer.

 

[4570Man]

Did you verify the brakes actually worked behind the F-150 and weren’t just disconnected? In any case I think it’s a relatively simple wiring issue.

 

[mrmikey]

I just put electric brakes on my trailer that I tow with a 2015 Frontier. It's prewired from the factory, all I had to do was mount the controller and plug in the harnesses to the truck wiring. Looking thru the instructions, there was a warning that some year Frontiers had the constant 12V and the trailer brake output inserted into the wrong side of the plug on the rear of the truck from the factory. Sure enough, mine was one of them so I had to reverse the two wires, not a big deal but it would have been a head scratcher for a bit 'tll I figured it out. Symptoms would have been the same as yours..........Mike

 

[Redlands Okie]

A few years ago we had quite a few issues with swapping trailors between ford and dodge. On my dodge the running / parking lights would lock the trailor brakes. The two wires were opposite. I have a factory made adapter plug that I use when I run into this problem. Save me from having to rewire some one else’s trailor to temporarily use on my dodge. A rental yard I use a lot has ford trucks. The last couple years the problem seems to have mostly gone away. I assume that most use the same wiring pattern now.

 

[skipperbrown]

You need to get a voltmeter and a helper and check each pin to see when it has voltage and confirm your ground pin. My guess is that you have incorrect wiring on the trailer but you will need to know when/where voltage is coming out of your truck and where it is going on the trailer.

 

[ovrszd]

A few years ago we had quite a few issues with swapping trailors between ford and dodge. On my dodge the running / parking lights would lock the trailor brakes. The two wires were opposite. I have a factory made adapter plug that I use when I run into this problem. Save me from having to rewire some one else’s trailor to temporarily use on my dodge. A rental yard I use a lot has ford trucks. The last couple years the problem seems to have mostly gone away. I assume that most use the same wiring pattern now.

Yep. I've saw this before. Some Fords didn't follow the standard wiring schematic. The suggestions and diagrams above will resolve the problem.

 

[mrmikey]

There was a thread here I think it was years ago. It was a four way stop intersection that a 1500 series truck pulling a trailer went thru and hit a car. The truck driver said he tried to stop but the weight of the trailer pushed him thru. The skid marks for the trailer were dashed, similar to a broken crossing line on a highway only black rubber skid marks, whoever had wired the trailer up had wired the lights to the turn signal circuit and the brakes would pulse with the turn signals. The driver said he had never needed to panic stop since he had the trailer and never noticed it before..............Mike