Coolant on the Passenger Floorboard – ’65 Chrysler 300 Factory AC

While cleaning the car up this morning for a show tomorrow, I noticed the passenger floorboard was wet. Turned out to be coolant. The question is: heater core (god, I hope not) or temperature control valve? The drip tray below the temperature control valve was wet with coolant so I'm hoping that is a good sign. How can I tell if it is the heater core or control valve?

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Author: rexus31