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Generally the front blinker and the dash blinker are powered by the same wire.
Rear blinker is on separate wire.
This is per side.
So I assume the dash board right blinker light is working, this means the problem is in the wire to the right front bulb not in the turn signal stalk.
If you have a volt meter or test light pull out the front bulb and turn on the blinker.
test for voltage, on and off of course, at the socket and use the Frame or other ground, not the sockets ground, because that could be the problem, loose or broken ground wire for that bulb.
If there is no power at the socket then you will need to start tracing the wire
Wiring diagram here: http://www.therangerstation.com/tech...top_hazard.JPG
Ford doesn't change wire color often, so the W/LB(white/light blue stripe) wire will probably be seen at the right hand bulb socket(Passenger side), if not then trace the wire color that IS there back to cab.
And just as a heads up, recently I have gotten 2 bulbs that were bad, new bulbs, chased my tail on that for a bit, tested bulbs and found out they were bad.
So never assume a "new" anything works.
So test with battery or swap it with other turn signal bulb.