Need some turn signal school

The turn signals get power through the ignition switch. Check the red wires on the switch inside the column or the connector just outside the column. You may just have a dirty connection or a broken wire. You should have power when you turn the key to run not start. For your purposes teh Duster and Valiant are the same.

Plymouth All Models Parts | Ignition Switch | Classic Industries

Turn Signal Switch without Tilt Column for 73-79 Dodge Plymouth Chrysler 191213402900 | eBay

http://www.mymopar.com/downloads/1973/73ValiantB.jpg

http://www.mymopar.com/downloads/1973/73ValiantA.jpg