I have a 2000 F150 4x4, I had a Rear Passenger turn signal go out on me. The bulb was intacked but I switched it any way, still nothing, then I replaced the socket. Didin't work either. So then I checked the wires all the way back to the ground on the frame. I unscrewed it and cleaned it up and put it back, nothing different. A few months later the the turn signal to the left flashed the Front Drivers and also both the Drivers Rear and the Passenger Rear, as if the hazards were going off in the back but not the front. Odd!!! I then read some forum on here about the multi switch. They mentioned to move my steering colum all the way up and try the blinkers, I did that and when I signaled the Right blinker it would some times freeze, but it was speratic. So I figured I had a lose wirer like some of the other guys. I had a few lose wirers so I took all of the wires out of the top gray plastic harness and plug them in directly to the multi switch to make sure they were connected. I still had the same problem (Signal to the Right: Rear Passenger no flash, Front Passenger flash rapidly fast. Signal to the left: Drivers Front normal, and the odd hazards going on in both back lights. By the way if it maters the Hazards worked on thier own normal this whole time.) I purchased a new multi switch and I now have a new problem the right blinker does not rapidly flash no it just does the same thing as the left signal, the odd hazards in the back. I plug in the nold one again and now I dont have any right signal and the laft does the same odd hazards in the back. This is an electrical nightmare any help please!!!!!

 

I was pretty much having the same problem, posted on here but it was of no help.. right now my left rear turn signal does not work and my left front turn signal flashes quickly. I replaced the bulb, checked the socket, replaced the fuse and still does not work...

 

My right turn signal is blinking fast and the bulbs are good. What else can I check?

 

Did you use some dielectric grease when you installed the bulb?
Might not help but it won't hurt.

 

In my case it was a broken wire. Check for broken wires.