I don't know how useful this is , or if it is the same flasher box thing that you were talking about. I have a 92 Mustang LX 2.3 4cyl. as well. I've had to replace pretty much EVERY lightbulb in the car except the interior roof panel.
When we changed teh fuses in the box and the bulbs in the dash but my turn signal still wouldn't comeon.. we had to purchase a flasher box thingy from Kragen autoparts..
It was under the console behind teh glove box, once we changed that the signal worked. though i don't hear a click noise every time the light flashes.
I don't know if it was supposed to make a click noise or not, but they work now!!
Good Luck, you'll need it! | 
