FYI the power goes to the flasher first before it goes in the column so that it then be switched between left and right. If power went to the column first to be switched between left and right then you would need two flashers one for left and one for right.

 

I am having a similar issue with my sons mustang. I have flashers but no turn signals. I have swapped the flasher module and both work on the flashers but neither make the turn signals work. I have verified the fuse is good and have replaced the turn signal switch. Any ideas?

 

Hmmm, well mine turned out to be the switch, I replaced it and the turn signals work fine now. Have you tried the rest of the testing suggestions from this post? My switch went inside the steering column and included the hazard switch and the cam and the whole wiring harness. Did your '72 switch have everything too?