Yeah, that "in the heater box" threw me - but the resistor was "on" the heater box, and the connectors are now mated. And the radio was already out to replace the defroster grates. Thanks to all for your suggestions and help.
Buddy I have the exact reverse of your problem. The harness with the black and brown wires that connects to the resistor is there but I don’t know where to connect the wires to!