There could be several answers, the first thing to do is to check to see if the (turn signal) fuse is blown. If that is the case - replace the fuse. If the fuse is ok, then the cause could be that the "relay" may need replacing. Other than the actual turn signal mechanism you should be OK.
2002 ford explorer turn signals not working
There are a couple of reasons why the turn signals will not work on a 1998 Ford Explorer. The light bulbs may need replaced or a fuse has blown.
Defective Flasher Relay.
If your 1999 Ford Expedition has turn signals that do not work but hazard lights that do work, it is likely that you have a fuse that is blown. You might also have a wiring issue including exposed wiring.
Check your fuse!
hazards and turn signals have separate flashers. replace flasher for turn signals
If the 4 Ways/Hazards are disconnected then neither will work the park lights nor the turn signals.
1. Bulb 2. Fuse 3. Flasher 4. Turn Signal Lever
Check fuse and turn signal flasher relay.
Check/replace turn signal flasher
the most common thing is a faulty multifunction switch.
Check the Fuses real quick. If not it could be related to a computer issue... Thanks Ford lol