If this Charger SE has tilt steering, the black with white tracer wire connected to the heater/air conditioning control now is likely C1-12BK* which originates at the steering column through an inline fuse. In this case, the C1-14BK* black with white tracer wire is unused and was originally supposed to be taped back in the harness. The tape back operation may have been missed, or it has been untaped and exposed over the years. This wiring can be seen in the following image:
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This wiring is shown in Figure 20 on page 8-152 of the wiring diagrams in the 1972 Dodge Chassis Service Manual.
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To verify that this is the unused C1-14BK* black with white tracer wire, with the battery disconnected, check for continuity between the loose terminal and the heater/air conditioner fuse at a the accessory bus bar in the fuse block.
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