first trailer hookup on the new truck - wiring issues
 

Hi all. I brought the trailer home this weekend to hook it up to my new 2011 F150 (EcoBoost with the Max Tow package). When I hooked up the 7 pin harness, I first got a "trailer wiring fault" error on the in dash screen then it said trailer disconnected. I thought maybe I hadn't seated the plug all the way. I've double checked and it seems to be plugged in well enough. I don't get the wiring fault error anymore but if I slide the brake controller on, I get the error popup screen that says trailer disconnected. I have brake lights and turn signals.

I used my multimeter to check the plug on the trailer (disconnected from the truck). I put the red probe into the power pin and tested all of the others (except the ground...didn't want to short something out) with the black probe. I get a good 12v on the turn signals and the markers, but on the trailer brake pin I only get like .32v. Is that normal? I figure there isn't supposed to be voltage to that pin except from the truck when the brakes are applied.

Then I tested the truck side with the multimeter and get 12+v on every pin (not the brakes). Then, as the brakes are applied, I get around 8-9v (same thing if the brake controller is engaged).

I jacked the wheel up on the trailer, spun the wheel and when the truck brakes are applied, I don't get any trailer brake engagement. I unhooked from the truck, spun the wheel and pulled the trailer brake emergency pin but still get no brake engagement.

So, to me, it sounds like there is something wrong on the trailer side beyond the plug. Sound about right? So, what would the right plan of attack be? What and where can I test continuity and try to track this down?

Thanks guys

Here's a thread just practically below your's for voltage references. I agree that it's probably trailer side.

You should hear a hum at each wheel if you are getting proper current. The magnet that moves to activate the brakes in the drum will also click.

Check this thread below.


https://www.ford-trucks.com/forums/1...ontroller.html

Have you installed the relay that's kept in the glove box?

So you get voltage on the truck side brake pin as the controller is applied. That is good! So now work your way back from there on the trailer side. Plug in the trailer. Do you get brake voltage on the trailer wiring close to the plug? Keep testing thru the break away switch all the way to the magnets. You'll find the short eventually. :)

If you place an amp meter in the line between the emergency pin and the wire to the brakes, it should read 12--about 3a for each wheel--when the pin is pulled. No amps to me would indicate there is no power from the batteries to the pin, or you have a break in the feed to the brakes. Partial amps would indicate 1 or more brakes not working.
These are maddening to trace down.
Joe

a lot of times they run the brake wiring thru the axle. That wiring tents to get hung up and break right around the springs and such.

Quick test as referenced above is a hum at each wheel on the trailer.

Have someone step on the truck brakes and you listen at each wheel on the trailer.

Huh? Not something I am aware of.


Thanks all. I'm going to continue tracking it back from the plug.

relays are under the hood at the power distribution box...the big fuses. check your owners manual

That relay may no longer in the glove box as it is a 2011 truck....it's prob "new to him". You may have to get a relay from Ford (or where you bought the truck). If you don't have the OWNERS MANUAL you can get one from Ford.com - I think it is /owners. Downloadable.

Just do this to start with. Unplug your trailer, but leave it hitched. Now with a charged battery on the trailer, pull your break away pin and try to pull the trailer. If the brakes are holding it, the problem is at the truck. If the trailer brakes are not engaged, the problem is with the trailer. Make sense?

Steve

Perfect! I have disconnected the brakes from the harness and have an open circuit through the black and white wires. I guess my next step is to remove each brake at a time to find my open.....

Look at the rear side of the drums for the wires that need from the axle to operate the brakes. There might be one that is broken.

I checked the drums and axles and all good. The problem was the wire through the coach to the front axle. I ran a new section of wire and now all good. Woo hoo!

Good to hear you got it fixed. Good job! :)

Steve

Thanks! We drove a couple of hours yesterday and the brakes and controller worked great. Trailer brakes come in handy when you have to stop in a hurry.