So, when I got this truck I thought "cool, the previous owner put in an aftermarket brake controller." I've never tried to use it until last week and sure enough, it's wired up all goofy.

It's a Draw Tite Activator II controller, and it's connected to the built-in harness with that common adapter you can get at etrailer or whatever. the truck did not have the full harness all the way to the back, so they (correctly) pulled a fused 12v hot lead to the 7-pin for power, and (incorrectly) spliced the wrong "blue wire" in the harness to the 7-pin.

there are two "blue" wires in the built-in controller connector - a 12g blue wire and a 16g blue with red stripe. The big blue is the output from the controller, and the blue/red was supposed to provide the signal TO the controller that the brake was being pressed.

Under the hood, the installer hijacked the blue/red wire and ran it back to the 7-pin. This "seemed" to work, as it provides 12v to the trailer, but theres no graduation - it's wide open immediately - and the wire isn't sufficient gauge to run the brakes.

Long intro to here's the problem ... I have no idea where that blue/red used to go, so I can't put it back the way it was. Secondly, now that it's been cut, if I pick up the big blue wire, it's also full hot immediately on pedal press. Disconnecting the brake controller completely doesn't interrupt the circuit - it seems the trucks internal wiring is set up to deliver 12v in the big blue wire even if there's no controller plugged in at all.

I can't make any sense of this, can't find a good wiring diagram anywhere, and the internet is flooded with forums about how to wire it up, but nothing fully explaining how the existing wiring was/should be configured.

Anyone have a brake system wiring diagram? Anyone have ideas on how to put it back the way it was?

I'm not kidding - I've spent hours looking at where they spliced into the blue/red, under the hood, in the big connector by the master cylinder. I'm going nuts but there's no evidence the wire ever went anywhere. In fact, it seems to poke out of the black tape wrap and as best as I can tell it's the factory wrap. Is it possible that blue/red was originally just hanging out dead-ended there and they picked it up, and it never originally went anywhere?

Losing my mind...

 

I'll go look at my '13 to see if I can help, but meanwhile the Activator 2 is a time-based controller and a POS (sorry). It's probably either turned up all the way or internally shorted due to mis-wiring, which is why you're getting a straight 12V out of it.

 

Hopefully the answer will help if anyone finds this thread.

In the 2011 XLT (and I'm sure many others), if you did not get the full tow package, it seems Ford saves a few bucks by stripping wires from the harness from the engine compartment to the back bumper. Such was the case here.

There is a large connector near the master cylinder - you can clearly see it comes from the firewall and then turns and most of the wires go to the back of the truck.

The big blue wire from the engine compartment does not continue to the rear of the truck. It must be cut, spliced into new wire, and fished back to the 7-pin connector you've added. Additionally, a fused link should be pulled to the rear. Most folks would agree this should be a fused link picked up directly from the battery, however if you like, the big orange wire in the same connector is intended for this purpose. If you use the orange wire, no fuse is require as it's already fused in the box.

Now, here's where the installer went wonky. Poking out from the wire bundle is a small blue wire with a red stripe. It appears to just stick out and is dead-ended. This is the wire that provides brake signal to the port under the dash. You must connect this wire to something that gets voltage when the brake is pressed. I piggybacked on the hot wire that carries brake light signal to the rear. In the adjacent connector/harness, it's a grey wire with a brown stripe.

That's it. Brake signal from the grey/brown wire spliced to the blue/red wire, pulled two fat wires to the rear to add 12v and brakes to the 7-pin, and Bob's your uncle.