My rear turn signal quit working. It makes the quick blinking sound and all three of the other signals still work. This signal also won't flash hazards with the other three that do flash hazards. But the exact same bulb will light up when you turn on the headlights, just won't blink signals.

It's not the bulb because I've replaced it and also tried swapping with the other signals.

I watched a video about some sort of box on the driver side dash, but I'm thinking this might not be it because all the other signals work.

Hoping to get trusty rusty fixed before I get in a wreck.

 

1999 thru 2011 Rangers use a 2-wire setup for rear turn/brake lights
1 wire for left side and 1`wire for right side for turn/brake

So turn signal and brake lights use the same wire and filament in the 2 filament bulb
Other filament is for Park lights
So one bulb but 2 filaments(lights) inside

If the Brake lights on both sides work then the turn/brake bulb is OK, and its wire from the cab is OK

So non-working turn signal in the rear means the problem is in the Multi-function switch, the Turn signal stalk, it does wipers, high/low beam, brake, 4-ways and turn signals, so "multi-function switch"

Not hard to replace
Remove the clam shell covers from steering column
Unscrew the multi-function switch, unplug its connectors
install replacement switch
Test

 

It was the socket the bulb plugs into. The voltage indicator showed the signal in the socket plug and even the socket. So I wiggled the bulb and it worked if the bulb was at the right angle and pressure. So I bought a new socket for $16.