I have a 73 Duster that I just purchase and the heater blower would not work. I pulled instrument cluster to get the wiring and there is two plugs that looks like it would plug into the fan switch . One plug has red, black, green, brown and seems to be coming from main harness and has power with car switched on. The second one has just brown and green wires and no power and seems to be a stand alone harness just for the heater box. I would think that the plug with the power would plug into the fan switch. But I don't see anywhere to plug the second one into. Am I missing something a relay maybe ? This is a A/C car.