This is more a follow up with the issues people were having in this thread - https://www.f150forum.com/f118/trail...oblems-316625/

History:

Since I have owned the truck I have had nothing but issues with the trailer brake controller on my truck. I haul my car to shows/tracks all over the east coast and going through the mountains without trailer brakes is no fun! The standard electric brake option on the controller has never worked with my 18' flatbed with electric brakes. Originally it kept going back and forth with "Trailer Disconnected" errors. Dealership insisted it was the wiring on my trailer even though the trailer worked fine with the 2010 f150 I had traded in for the new 2015. So I went and replaced the trailer main wiring and junction box which did not resolve the issue Finally after doing my own searching I convinced them to do the software update to the controller. This atleast corrected the trailer disconnect errors I was constantly getting. The electric brake option in the controller still did not work. I took the truck and trailer up to the dealership and they hooked it up to two brand new 2016 models and still could not get the brakes to work. So they insisted it was an issue with the trailer still even though I can get them to function on my freinds Dodge and Nissan trucks. Only brakes I was able to get was by switching the controller over to use the "electric over hydraulic" option which is about 1/2 if not a 1/4 of the braking needed... but it was something and it also tells bme the trailer brakes were fine and it was indeed something with the controller. Dealer finally agreed and after multiple calls to Ford it basically came down to the controller not being compatible with my brakes and I ened to install an aftermarket one. WTF Ford!! It's a simple single axle electric brake set-up and I'm told my $40k+ truck with the tow package is not compatible with it!!

I finally broke down are starting doing some research and found that the brake controller uses a pulse signal that allows the system to detect whether or not the brakes are connected and functioning. It is all based off of load. If the system does not see the required amount of load then it does not think the brakes are connected/functional. So at this point my assumptions were that the resistance on the trailer was outside of the bounds of what the controller is programed to look for which is why it is not sensing the brakes are connected. Easy way to test was to temp increase the load the system would sense to see if that would trigger the brake controller to sensing that the brakes where indeed there and functioning properly. Using a load resistor which is what is used when you swap out to LED lights was great for testing out this theory:



So before I installed it I checked the resistance of the brakes. Just the brakes and wires tested from the junction box I had about 3 ohms. Installed the resistor as seen below and I now had about 6 ohms.



Hooked up the truck, changed the settings over to "Electric Brakes" and the controlled for the first time connected to the trailer! I tested the manual override and it locked the trailer brakes up like it should have. So finally after 2 years of fighting with the dealership and Ford I have resolved the problems on my own.

**Note - After I confirmed it was all working I mounted the resistor to the trailer frame as it does get warm/hot when in constant use. So be sure to mount it away where it can stay cool.


So to sum things up if you are having the trailer disconnect issues then force Ford/Dealership to flash the brake controller to the newest software. Not sure what year the newest software went into the production line but that is the first step. Fords brake controller is very sensitive to minimal changes and disruptions. So be sure your connections and good and clean. My trailer was not even 6 months old so I never should have believed them about the wiring issues and wasted my money replacing what I did. if your electric brakes are not being sensed by the brake controller than it is likely that the load is too low and the brake controller is just not picking them up. IDK what the minimum the controller looks for but it is obviously set too high from the factory. So try the load resistor like I did and see if that solves the problem.

I'm hoping a Ford rep see's this and actually takes action to resolve the problem as I know a lot of people with the tow packages have issues similar to this with their trucks.

 

Super, super helpful! Thanks for doing this. (I never would have figured that out....lol!)

What type and brand of trailer was it?

 

Great thinking!

 

Local built trailer. All electrical components, brakes, etc you can buy right off the shelf at Tractor Supply. So not like any of it was anything special. Just Ford over Engineering **** again.

 

Great detective work!

 

Two questions:

1. Are the parameters for the brake controller adjustable in FORSCAN?

2. Did you wire the resistor between the brake wire and the ground, or is it in series with the brake circuit?

 

I had your exact issue with my new TT, I took it to the dealer and they reflashed the TBC and everything works great.

 

No clue on FORSCAN. Never bothered looking into it and didn't want to deal with it. Tired of dealing with Ford/Dealership not having a clue about it. That's what happens when you over complicate ****, Nobody knows what it does or how to fix it.

Resistor is wired in parallel between the ground and brake wire. You want to increase the load "Ohm's" so it has to be in parallel.

Had mine reflashed twice, new plug installed, Etc. The towed my trailer into the dealership and they tested it out and hooked it up to other brand new trucks and none of them worked. So it's not an issue specifically with my truck, it's a design flaw in the brake controllers Ford is installing in the newer model trucks. My 2010 didn't have this issue and neither did any of my aftermarket brake controllers. Buddies 1500 worked fine also.

 

yeah I flashed the latest calibration and it solved this issue.

 

If it's in parallel with the brake magnets, you have reduced the resistance the controller sees. The total brake resistance was 3 ohms before the resister was added (trailer magnets are often 6ohms each, so two wired in parallel are 3 ohms at the junction box) and you added another 3 ohm resister, IN PARALLEL with the brakes, you have halved the resistance and doubled the current. You should be reading 1.5 ohms, not 6 ohms.

http://www.electronics-tutorials.ws/resistor/res_4.html

Resisters in parallel have the relationship:
1/R1 + 1/R2 = 1/Rtotal

It sounds like the brakes on your trailer are wired in some kind of series/parallel combination or completely in series, that is making the resistance too high and the controller flake out. If any of them are in series, if you loose one brake, the rest stop working. Wiring isn't always a strong point for trailer builders, so I would have a closer look at how they are actually wired up. Many controllers are less "smart" than the Ford unit and don't care as long as some current flows.

4 trailer brakes, properly wired in parallel, should show 1.5 ohms at the controller.
The updated programming probably allows for a greater range in the allowed resistance which is why the disconnected warning stopped happening.