Trailer Brake Problem, I'm out of ideas

[Mike Higbee]

While on vacation 1000 miles from home we made a quick stop and when I restarted the Expedition the travel trailer brakes were locked up solid. I checked all of the obvious stuff and finally just disconnected the trailer power cord and drove to our immediate destination. After a bit of trouble shooting but no cure found I pulled the brake module fuse #18, reconnected the power cable and at least had all of the necessary lights, turn indicators, brake lights etc. but no trailer brakes.
We limped back home and after spending the day cleaning ground terminals, checking connections etc I've made no progress. I purchased a LED connection tester and it shows that the brake lead is hot all of the time even when the ignition is off!!. The 12volt charging lead is hot when the engine is running and not hot when the engine is off. I'm stumped, if the brake circuit was getting juice from the 12v charging wire due to a short, corrosion or frayed wire it wouldn't be hot when the ignition is off and the 12v circuit isn't hot. Any thought or suggestions would be greatly appreciated.

 

[Gary Waugh]

Sounds like the electronic brake control has failed. Are you running an aftermarket controller or a ford controller? I would disconnect the 4 pin plug that goes to the brake controller and then check if you still have 12 volts present at the trailer brake pin. If you do then you have a wiring short to positive, if you don’t then the controller has probably failed. you can then replace the controller to get yourself home and then perhaps see about getting the old controller fixed once you get home (keep it as a spare). Some aftermarket controllers are not very well protected, so if your trailer brakes try to take more current than the controller is rated for, it can cause the controller to fail (either something shorts keeping the brakes on all the time, or something pops causing the brake output pin to never go positive (no trailer brakes)).
Anyway I would suggest disconnecting the trailer brake controller and see what the power pin to the trailer brake does, and go from there.
regards Gary

 

[Mike Higbee]

Thanks Gary, the controller is the integrated factory unit that comes on the HD tow package on Platinums. I had pretty much decided that the problem was in the controller. I'll try your suggestions

 

[Gary Waugh]

Mike, I assume you know this, but in case, there are 4 wires that go to the Brake controller, one wire is +12 volts (usually coming from fuse #18), one wire is ground, one wire is from the brake switch (activated by the brake pedal), and the 4th wire is the output wire from the controller that goes to the trailer plug at the back of the car and powers the trailer brakes.
If you have a voltmeter, it should be very easy to disconnect the controller, then verify that you have the 12 volts, the ground and that the brake switch goes to 12 volts when you press the brake pedal. Then with a resistance range, check that the controller output wire is not shorted to 12 volts or ground (do NOT cponnect the trailer as the electronic brakes will make it look like the controller wire is shorted to ground).
If everything is good, then the controller has failed, if something doesn't check out, then find the cause and fix it, your controller might still be okay.

 

[Mike Higbee]

Gary, thanks for the additional information. I've ordered a new controller that should be here in a couple of days. Then I'll tear into the dash to see what I can see. If I discover a wiring fault I'll toss the new controller in the pile of spare parts to go along with the spare throttle body that I keep on hand. If it's the controller I'll replace it. The Expy is our primary transportation so I can't have it torn down for several days.
I wasn't aware of how the controller is wired but your explanation is pretty simple. I'll scout around on the web and see if I can scrounge up a wiring diagram. I'll post back what problem I find. Thanks again

 

[Mike Higbee]

Gary, the new controller showed up today but didn't look like I thought it should so I pulled the radio fascia off and popped the controller out of the dash. The part I received was totally different then what is installed in the expy so back it goes. In the meantime this is the plug on the controller with six wires. I'm assuming the larger gauge blue wire is the wire that goes to the trailer to activate the brakes but the remaining wires are a mystery. Seems like if I disconnect the plug and apply the VOM to the contact that matches the blue wire it should not be hot if the brakes aren't applied and if it is hot then the controller is faulty, any thoughts

 

[Gary Waugh]

I suspect you need someone with a more modern expedition. Mine is an 08 and only has 4 wires (but it’s an aftermarket controller, I don‘t think ford offered factory controllers back then).
my guess is that the 2 large wires (yellow and blue) are the main 12volts in and the trailer brake wire out. That leaves the 4 smaller wires, one must be the brake pedal switch, another must be ground, but I have no idea what the other 2 are, 1 is probably connected to the lights so your controller facade lights up when the headlights are turned on, and no idea about the last wire..
hopefully someone with knowledge of the later controllers can help out.
You should still check that one of the large wires (yellow and blue) is live all the time (has 12 volts present) and that the other wire just goes to the 7 pin trailer plug and does not have any connection to positive or ground (again with no trailer connected) to make sure you haven’t got a wiring failure.
sorry I can’t help more..
Gary

 

[Mike Higbee]

Thanks Gary, you've been a great help, I agree the smaller gauge wires must be lighting or perhaps solenoid controls as they are too light a gauge to be carrying much load. I'll check the two larger wires and see where that leads me.