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Discussion Starter #1
I did some searching around, but I didn't find any definitive answer to my question, so I hope someone here can answer it or post a link to a thread I missed. Or maybe even know a place where I can get it repaired and save myself some money ($300 for a new controller).

2006 F350 6.0L factory brake controller. Shows no faults--actually appears to be working, but my wife told me to check the trailer brakes (brand new installed last year) because she said they didn't feel like they were engaging. She hauls a two horse goose neck trailer, and she's been hauling horses for over 15 years, so I trust when she says something doesn't feel right. Anyway, The bars scroll across the bottom when you push on the brake pedal and everything, but the brakes don't engage. We pulled the trailer up on the ramps, I spun two of the tires, and she hit the brakes. Nothing but a slight hum from the magnets in the brakes. I spun the wheels again and she hit the manual override and the wheels locked right up as expected, and a very noticeable and louder hum was heard.

If I understand how these controllers are hooked up, I believe the brake pedal sends a signal to the controller, which is then amplified and sent to the plugs on the back of the truck. Correct? She has a plug tester that has LEDs for every function of the 7 pin plug. When you use the brake pedal, sometimes the brake LED flashes and goes out or stays on, but it's really dim. With the manual bypass it's as bright as the other LEDs (left and right tail lights, 12V, etc).

So, I believe I have it narrowed down to the controller itself. I even took the lower dash apart partially to look at the wiring to check for anything loose, broken, worn, etc. I'm ex-Navy nuke electrician and now an Electrical Engineering Technician, so I'm quite familiar with electrical troubleshooting, but I wanted to get your guys' input on this matter. I'm good at what I do, but I may have missed something. Oh, and we did check all fuses associated with the brakes and controller. We have a print out of all the fuses and anything that had "brake" in it, we checked.

Thanks in advance for your help.
 

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If she runs trailers like you said, I'm sure she's got a friend out there with a brake controller. Ask to borrow it for a test and see if the known good controller fixes your issue. If it does, you've nailed your problem. If not - you get to keep searching.
 

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I believe the software on the 2005-2007 reduces brake current to a minimal amount with zero vehicle speed and ramps it up to normal amount as you speed up to 12-18 mph. One of my 2006 trucks has factory controller and I can roll the wheels with some effort if someone depresses pedal and I spin a jacked up trailer wheel.
The other thing to check is what is the voltage on the ground side with brakes applied full with manual lever. IF you see over 0.3 V on the ground then clean/repair grounds. Ohm meter inspection of grounds is NOT ACCURATE. One strand of wire connected will show 0.0 to 0.4 ohms but you will have very low current flow (and high voltage reading) on the ground side when the circuit load is present.
 

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Discussion Starter #4
If she runs trailers like you said, I'm sure she's got a friend out there with a brake controller. Ask to borrow it for a test and see if the known good controller fixes your issue. If it does, you've nailed your problem. If not - you get to keep searching.
I would have done that if we knew someone with a 2005 to 2007 who also hauls. I have one friend with a 2007 F250, but I don't know if he's still in the area. You're right though in that is the ideal way to guarantee it's the controller or not. I told my wife that, but from what I'm seeing I don't know how it could be anything else. I really don't want to get an aftermarket controller, even though they're cheaper. I like the clean look of the inside of my wife's truck.

I believe the software on the 2005-2007 reduces brake current to a minimal amount with zero vehicle speed and ramps it up to normal amount as you speed up to 12-18 mph. One of my 2006 trucks has factory controller and I can roll the wheels with some effort if someone depresses pedal and I spin a jacked up trailer wheel.
The other thing to check is what is the voltage on the ground side with brakes applied full with manual lever. IF you see over 0.3 V on the ground then clean/repair grounds. Ohm meter inspection of grounds is NOT ACCURATE. One strand of wire connected will show 0.0 to 0.4 ohms but you will have very low current flow (and high voltage reading) on the ground side when the circuit load is present.
What would be the point in reducing braking pressure with the vehicle not in motion? Either way, she knows the trailer brakes aren't working at speed, so I'm pretty sure it's safe to take her word on it and skip that step in the troubleshooting process.

I think I might just get on FB and see if there's someone nearby that may let me swap controllers for a day or two. There's a dude on ebay, I believe, that refurbishes the factory controllers. You pay him like $80 for a refurbished one and send yours in as a core. I'll check that route first whenever I determine for sure the controller is at fault. I was hoping someone here had the same experience and could give me a definitely yay or nay. Thanks for the info, you two. I appreciate it. Oh and the ground checks isn't a bad idea. I may do that as well.
 

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Electric brakes are grabby if high current is applied at low speeds. How many times have you had brakes turned up on a heavy trailer and had the brakes be "touchy" or slide the instant the brake pedal was touched and controller applied brake current? Prodigy and others have "boost settings" that are their efforts to prevent this. High current to magnets heats them up and does nothing beneficial if you are stopped. Deceleration sensed systems already do this as they will have no decel input when you are still.

The low hum with pedal, high hum and lock with manual lever is how my truck works but the brakes on trailer work as they should at speed.

Have you adjusted brakes? I would think a 2 horse trailer has 3500 or 5000 pound axles and those rarely have self adjusting feature.
 

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Discussion Starter #6 (Edited)
When I replaced the brakes all I did was swapped out all four entire assembies and soldered and heat shrunk the wires. The person at the trailer place told me it was all I needed to do. "It's so much easier to replace the whole assembly than just do the shoes...doesn't cost much extra either..." she said. I'll pull the wheels this weekend and take a look.

But here's the thing though. My wife just reminded me that we hooked up her mom's trailer to the truck and got the same result. I spun the wheels by hand, heard a low hum, but the brakes didn't stop the wheel, but the manual override maybe half engaged locks them up (according to my wife) without a problem. Does the manual override bypass the setting you place on the controller? She says it was on 6 when she did the override.

Also, your explanation of the low current when stopped makes sense. I do hear a light hum on the brakes and the LED on the trailer plug tester sometimes comes in dim or flickers. Do you think if I jack the rear of the truck up (jack stands) and simulate moving it'll allow me to better test the brakes on the trailer? I could pull the wheels on the trailer and make adjustments. My wife says she can't tell if the trailer brakes on her mom's trailer are wrong because it's such a smaller trailer that her truck can stop it without issues, even loaded down. That's what she claims anyway. She never hauled her mom's trailer back when we know for sure the brakes were working (before I replaced the brake assemblies).

What a pain.

Sent from my SM-G900V using Tapatalk
 

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The backing plates you changed will have adjuster holes covered with oblong plugs you pry out. The brakes need adjusting when installed and periodically thereafter.
There has to be youtube howto videos posted to show you the way they are adjusted.

The manual lever is independent of the settings on controller that adjust the brake current for foot pedal application.
 
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