Turn signals died

I have a 72 Charger and the turn signals just stopped working one day.
Here are the details:

Everything else works: hazzard lights, horn, brake lights, etc.
Replaced short, fat, two prong turn signal can (works with hazzard lights).
Checked contact on turn signal cam in stering column. OK

I found another can under the dash that is not as fat as the turn signal can. The guy at Pep Boys had no idea what it was and had nothing on the shelf that looked like it. It is a three prong can.

Any ideas or suggestions?