So the rear drivers side blinker/brake light is not functioning, however the parking light still works. The bulb is a two filament type and both filaments are fine, and if the bulb was bad I imagine the parking light would not work (parking light, brake light & blinker are all the same bulb). I thought it would be a fuse but I can't even find a fuse description that would fit this light. I found a turn signal fuse but that was fine. Any thoughts?

 

Had the same problem the drivers side turn signal would not work but the bulb looked fine. I swapped the bulb with the passenger side one and the problem followed the bulb. The driver side worked fine with the swapped bulb so I knew it was not an electrical issue. Purchased new bulbs and replaced both sides, kept the old one as a spare.

 

Thanks Jeep Hauler. Just performed the same diagnostic and you were right on, problem followed the light, i'll pick up a new one tomorrow. I know it is under $10 but this seems like something that would be covered under full warranty. Thoughts?

 

i have the same problem but the trouble did not follow the bulb the light works the reverse light works when i hit the brakes the whole light goes dark and when i turn on the left turn signal it all goes dark dont have a clue anyone know what it is?????

 

Becky, if u will retype that with punctuation or start a new thread, you will probably get an answer.. I am having trouble figuring out does the reverse light light up with the brakes applied or does the whole thing go dark.

I will be glad to help if you will help me figure out the problem.

 

sounds like what was/is happening to me. Found that ford had a recall describing just this type of problem. Seems covered in the recall 2003 - 2007 f250/350/450 is a short in the headlight mutifunction switch which overheats and warps the multifunction (turn,brake,4way,hi/lo) resulting in improper light operations. I am not willing to spend $160 for headlight switch, $140 for signal multifunction and $200 labor to have it maybe fail again. Ford won't do my truck under recall because I am not the original owner. Right now I have switches temporarily bypassed and am working on a plan to rewire for a permanent solution.

 

Sorry bout that the lite comes on when I start the truck when I apply brake it goes dark then I back up and it comes back on til I hit the brakes again.and the turn signal makes it go dark too

 

There is no definative way in which the mulfifunction switches fail. The common factor is that when they fail lights don't work as they should.
Before removing dismantling and examining/correcting my multifunction turn signal switch, with headlights off brakes and signals worked but turn on park or headlights, and parks come on bright, brake comes on dim and high-brake comes on dim. Step on the brake and high brake comes on bright, tail brake lights go out. Use turn signal and high-brake comes on flashing, and signal light at one side or another comes on dim and fast flash. I don't know why headlights have anything to do with signal/park lights/brake lights but I suspect damage to the security module (which controls headlights, parklights, keyless entry, interior lights, vehicle alarm, etc.) and a defective headlight switch and a damaged (warped contacts in turn signal pcb contacting hi/lo beam headlight switch).

As an Electronics engineer, (commercial/industrial) I see the entire layout of the multifunctions a source for problematic operation. In the one switch you have a 15A feed and a 30A feed supplying a DPDT slide switch for Hi/Lo headlight, A 30A feed and a brake switch feed and a 4way flasher supplying the 4way flash switch (a 5PDT) slider and the dual 3PDT signal Slider exiting along with the Wash/wipe 9P ground referenced switch. You wouldn't find this sort of thing in commercial, or Industrial electronics. How we would do it is to use 4 SPST independent switches fed by a single +12 0.1A source and do all the switching using relays under the dash. No complicated slides, no chance for close proximity shorts, plastic wear damaging or jamming the slides.

But that is just MHO. I will continue to design my new relay panel and switches to bullet proof my truck.

 

You are missing a ground for that light. The tail light will seek ground thru the brake light and when you put on the brakes or turn signal the path is lost.

 

I had considered this too as a possibility but could not find a bad ground so didn't think of it further in my response to the OP.

 

THANX everyone for the advice I'll let ya know when I figure out which one it is