2004 F250 super duty, 6.0L 4x4
This issue started today. I was driving home from work and noticed my trailer brake controller was going up and down and not turning off, and my brake lights were stuck on, all 3 of them.

I recently replaced my brake light switch so I started there. I unplugged it but my brake lights stayed on and my trailer brake controller was stuck on 15%. So leaving the brake light switch unplugged I unplugged the trailer brake controller. The brake lights were still on. So I looked into the fuse panel and pulled any fuse related to the turn signals or brake/exterior lights. The brake lights never turned off. I then turned to the forums and noticed someone mentioning a multi function switch, after a quick google search I tried turning my turn signals and the light that went with the turn signal turned off (Left turn signal on, left brake light off and vise versa) so I pulled my turn signal relay. Brake lights still on and the turn signal switch did the same thing.

s there a way I can easily unplug the multifunction switch to see if thats the issue?
Any other ideas would be great. Thank you!
Any temp solution to get them to turn off temporarily without having to disconnect the batteries would be appreciated too

**UPDATE**
Im sorry for the late check in. Ive been busy
After messing with the truck for a bit I realized this
While the truck is in the on or acc position the brake lights will stay on
After the truck is shut off completely the lights will stay on
AFTER 30 minutes of staying in the off position with nothing happening the brake lights will just turn off
Pretty much exactly 30 minutes every time
I also tried disconnection the headlight switch and the lights stayed on. I also went and individually disconnected all 3 of the brake lights (Left, right, and 3rd/upper brake light) and nothing changed
Im even more confused now lol but at least they arent staying on and killing my batt

Thank you for all the replies, I appreciate it very much

 

To the best of my knowledge, the multifunction switch can only be unplugged by removing the steering column trim shroud.

Did you also remove the trailer lighting fuses and relays, or just the ones for the truck?

A thorough visual inspection of the wiring along the driver side frame and the connectors at the tail lights may reveal the problem. It wouldn’t be surprising to find a harness short on an 18 year old truck.

 

Relays under the hood,
disconnect trailer wiring harness and see what happens would be my first move.

 

Just a wild speculation, but is there any potential that the wires for the brake light switch could have been worn or a short created somewhere, causing current to bypass the switch and activate the lights?

 

Check for short at trailer plug between battery and brake circuit, corrosion,moisture etc

 

This is probably related to why you replaced the brake light switch. What was happening before that prompted the switch replacement?

 

I had this on my '06. I found that the trailer brake controller was set. I must have bumped the slider switch and put the brake lights on. After I correctly set trailer brake controller, the problem never came back.

 

He explicitly stated he had disconnected the TBC with no change in the behavior of the stop lamps. Same for the BPP switch.

It should not be possible for a wiring fault at the rear of the truck to cause this issue. The trailer adapter stop/turn signals are isolated from the truck's stop lamp circuit by normally open relays.

He needs to disconnect the MFS next to see if the circuit short to power is in there.

You'd need to determine which fused circuit is improperly feeding the brake lamp circuit. It's supposed to be fuse CJB F18 fed through one half of the BPP switch.

If this truck's wiring is unmodified, the LG wire from the BPP switch should feed to the following: 3rd stop light, MFS switch, TBC, and the upfitter wiring bundle.

 

The brake lights were kinda working but kinda werent. They would sometimes stick on and the brake controller would also stick on. If I wiggled the sensor around it would work properly again. After replacing the switch it fixed the origional issue

 

I did try pulling fuse 18 (Turn lamps / Brake on-off switch (high) and the lights stayed on. I am still working on learning to disconnect the MFS. Im not super mechanically inclined when it comes this kind of stuff.

Thank you for the reply