My 69 Dart w/ factory AC had a hot water control valve, vacuum operated. It seems everyone is guessing about the OP's car since he didn't relate the model year or if factory AC. That always helps when posting a question.
In my early A's, I plan to add AC and may add a hot water valve. No great need since they will have a separate air box for AC, so little air flow thru the heater core, but would still help. I recall that my 69 valve just blocked the flow, but I recall photos of others with more hoses that I assume switched to bypass mode. Does anybody know?
