"Trailer disconnected" error message - F150

[RandyNH]

In your example, a 10w bulb was added to increase resistance to cause the trailer to disconnect, then "he could force the trailer to disconnect by removing the bulb" YES because he opened the newly bypassed ground path.

Your testing with the bulb, created a new ground path DO NOT ADD RESISTANCE to it, they did to cause a fault.

Do not look at the problem so hard that you over think it, these problems are almost always related to the ground connection between the TV and trailer. On some that can be the connector, on others it can be where in the belly of the trailer the cable terminates and connects to the ground point out anywhere in between and can be difficult to locate when this is the case.

Refer to my post #17 and PLEASE do not add resistance to correction, all you will be doing is making the new path closer to the point of failure.

To duplicate the trouble shooting tree you used as an example you would need to add increasing wattage bulbs to find out what level it takes before your setup show a failure of the circuit, his was 10watts yours is obviously higher.

Edit- generally when you get the intermittent disconnect this is usually indicating that the system is having to rely on the physical connection of the coupler for part or all of the ground for the braking circuit. Thus as the coupler shifts with the road flow it loses it.

Good luck and keep us posted

[TG Twinkie]

By adding the bulb you have not increased the resistance because it is wired in parallel with the brake coils. You have increased the load on the brake controller.
I would check not only the ground connection(s) but all connections at each wheel.
You could also have a bad brake coil, but that doesn't seem likely.
I don't believe your brake controller knows if you are towing a single, tandem or triple axle trailer.
The bulb may be faking out the controller giving you the idea that the brake circuit is OK. IMHO. You need to look into this further.

[Jekerrville]

TG, dead on! Your 'mantra' is what these forums are all about, IMHO. I believe OP has his answer. All the best.

JE

[RandyNH]

Well then in that case, I must apologize to everyone, it seems I misinterpreted the purpose of this thread. I was under the impression he was concerned about the brakes on his trailer working properly, I didn't realize he just didn't want the disconnect light to come on.
Realizing the error of my interpretation, you are certainly correct that by providing a parallel circuit that bypasses the brake circuit and provides enough resistance so the controller thinks everything is there, will in fact cause the error light to not illuminate.

Following this "troubleshooting" of this logic, I wonder if the OP would be kind enough to post a photo of his entire rig, as viewed from the front, so that if I ever see him in my rearview I can get the hell out of the way.

[Ruscal]

It sounds like Ford chose the wrong resistance value in their circuitry. Maybe it is too sensitive on the safe side which triggers an open condition when it really has plenty of conductivity to operate the brakes. ??
I installed a new OEM style 7 pin receptacle on the back of my truck. When I plugged in the Bambi it was intermittent. I cleaned all the pins and sockets with no success. I found that the way the Airstream plug was molded that it would not insert into the OEM plug enough to grab no matter how hard I pushed on it. I installed a new plug on the Airstream and it inserted properly and made good contact. I got to examine the original Airstream plug on the bench and tried inserting it into another receptacle I had. It would not insert. I believe the cause to be that the rubber plug had shrunk over the years, shortening the distance needed to insert properly. The airstream is a 2008, so about 9 year old plug. It may be time for some of you to swap out those older plugs if you are having blinking lights and open circuit brake warnings.
Russ

[travellvr]

Thanks again everyone for the good tips! Turns out that an application of dielectric grease on the connection solved the problem for me!

[dstalzer]

Originally Posted by travellvr

Thanks again everyone for the good tips! Turns out that an application of dielectric grease on the connection solved the problem for me!

I used dielectric grease on the connection of my 2005 Airstream and 2016 F250 and it seemed to work for a while. I just returned from a 2300 mile trip and got thousands of "trailer disconnected" messages while driving, and the trailer brakes are not working now. The lights on the trailer never blink off when the message occurs. After disconnecting the trailer from the truck while driving away without the trailer I got "trailer disconnected" again.

Dennis

[franklyfrank]

Originally Posted by dstalzer

I used dielectric grease on the connection of my 2005 Airstream and 2016 F250 and it seemed to work for a while. I just returned from a 2300 mile trip and got thousands of "trailer disconnected" messages while driving, and the trailer brakes are not working now. The lights on the trailer never blink off when the message occurs. After disconnecting the trailer from the truck while driving away without the trailer I got "trailer disconnected" again.

Dennis

After a while cleaning the contacts will not work and you will have to replace the plug on the trailer. I went trough the same drill with our previous AS. I begun to get intermittent disconnect signals, then I would fiddle with and clean the contacts and then the same thing.

[emelaich01]

Not only check the umbilical cord but on the back (revetse side) of the trailer socket underneath the truck, you may find that there is a separate plug that goes to the receptacle. We found ours loose and after reseatng the plug, all the lights and the trailer brake functions begin to register normally; take a look--might be a cheap fix!

[MWBishop]

My F250 once refused to recognize AS rear brake lights when connected.
Rebooted truck (turn off then restarted) and been fine since (so far).