Does your HVAC system have the horizontal or vertical button layout?
If it's the horizontal later version (as I think it is for your year), is the "solenoid valve" you replaced the monovalve, that's located on the firewall in the engine bay and regulates the flow of coolant into the system?
I ask because it sounds exactly like you've got a failure at that point. The default for the valve is open, and whether it's got a torn diaphragm or bad electrical connections, if it's not actively restricting flow you'll get unstoppable hot air.
From the department of goofs I might characteristically make: You did put the connector back on it, I assume.