As many of you who have owned these older F-150's have come to know that sooner or later something goes wrong with you truck in such a way that it leaves you stumped as to whats really going on, this would be one of those times and this is a problem I've had ever since I first pulled apart my steering column to replace the upper ignition actuator (cheap pot metal piece of junk). What my problem is is that I have only one brake light that's working at a time, I noticed the right bulb was not lit up with the brakes so thought to myself simple fix its just a bulb but as I turned on the the left hand turn signal the right bulb for the brake light lit up and and if I go to the right hand turn signal same deal which means that much is working properly but no matter what I do that right hand bulb does not work and if I move the turn signal in just the right spot it will switch sides causing the left one to not light up and the right one to light up just fine. I have a video of whats going on as well that once is down uploading i will link to to give people a visual of whats going on. I think its the turn signal switch having something to do with this. Anybody got any ideas cause I'm out and I've got two months until inspection time and I'm gonna be screwed if i can't get it fixed by then.

 

Video is now up
Brake light issue - YouTube

 

Sounds like you need to clean the turn switch. This is a common problem over the Ford RV site. They use the same switch.
Before cleaning:


After cleaning:






/

 

Probably wouldn't hurt it any, only thing is my column is one of the older ones where to get at the turn signal switch you need to take the steering wheel off. I'll be trying that in the morning after I finish installing the thermostat.

 

So after doing a boatload of research and asking a few guys around town about this issue I have narrowed it down to the multifunction switch in the steering column of my truck so I will be forced to strip it down once more and either find out why its acting up or replace the whole darn switch if I get sick of fiddling with it. Looks like I'll have to get that done this month.

 

Yep, you have a short to power. It could possibly be your wiring welded together, but since corrosion in switches is pretty common I would definitely start there.

 

I just got the old multifunction switch out today and there are no obvious signs of wires that were stuck together and the switch while it is not in the best of shape seems to show no obvious signs of corrosion, shame I can't inspect the contacts on the cam to see if they are the problem but When I put the turn signal cam in during the summer I glued the damn thing in place like the idiot I am some days.
I got another switch and I am getting ready to put the new one in as we speak but I will do like you said and check out some of the wiring to and from in various spots if this 50 dollar switch doesn't fix it like I hope it will.

 

Turns out it was the multifunction switch in the steering column, I just finished installing it today and the brake lights work perfectly now. what a pain in the butt that thing was to replace but at least it works good now. Come Monday I am gonna get the old girl inspected and have a fresh sticker on it before it try's anything funny.

 

Very good. Always a good feeling to fix an electrical problem on the first shot. Electrical diagnosis is a thinking mans game, not a parts changers job.