70 Dart non ac switch wiring.

I have a 70 dart swinger non ac and I am wondering if someone could help me with the heater switch wiring.

I see the harness that plugs into the resistor on top of the Heater box, but am not sure how the switch comes into play. The P.O. had the heater running off a manual switch, so I am not sure if the wiring has been cut somewhere.

I have a factory 70 dart service manual, but am having a hard time locating that diagram.

Thanks in advance!