I have a 2002 F250. It started out that when i put my right turn signal on i had a rapid blink so i figured i had a bad bulb. I checked the bulbs and they are all fine. Then it became that when i would put on my right turn signal it would just stay lit on the dash and there is a buzzing sound coming from behind the dash. I have also learned that my right brake light no longer works. But when i turn my parking lights and or headlights on the rear light works but wont get brighter when the brake is applied.

 

There is a connector near the back that is known to get corroded. It should be near the spare tire carrier and run towards the front of the truck and also branch to each tailight.

You also could have a bad bulb that is intermittenly making contact.

all turn signals brake lights etc go through the multifuntion switch (turn signal stalk). There is procedure for checking multifunction switch in my pics but i think it is prob much easier than that from what u described. Flasher is prob source of buzz.

 

Carltonwebb - I see you mention you have a procedure for checking the multifunction switch, can you help me find that? I can't figure out where it is or what it looks like to check it! New here - hope I'm not asking a dumb question!!

 

I had a similar problem on my '99 F-250. Started with turn signal not working when brakes were applied, ended up with no signals and a buzzing from under the dash. Changed the flasher relay (sg141c), problem solved. You have to remove the lower center dash section to get to it. Part was a Tridon/Novita Tech EP 27. $16 at my local parts store. Hope this helps.