A/C heater vacuum solenoid

I have a 1998 Explorer Sport and found a vacuum solenoid leaking antifreeze inside the engine compartment.  What is the vacuum solenoid that bypasses the heater core called when the A/C is on? It doesn't show up anywhere in the Haynes repair manual.

#2.. Water/Coolant Diverter valve, Water/Coolant control valve.. Depends on who you ask :)


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Or also I found out it was the "heater control valve".  Thought I had a head gasket leak due to a small amount of antifreeze consumed over a month.  Saw it dripping by accident as I was testing A/C fill.  This should be an easy fix.  Thanks for your response hayapower.