A/C blowing only hot air no matter what temperature is set

Can you hear the compressor kicking on? If the compressor kicks on and the lines are cool to the touch, we can scratch the A/C refrigerant system off of the list. Another possibility is the heater coolant control valve. It's job is to stop the flow of coolant to the heater core when the A/C cold air is selected and vice versa, I have replaced many of these over the years for similar issues and they're no fun! One way to verify that the valve is operating normally is to start the vehicle after it has sat all night and select max A/C with the temperature set to 60, after the engine has reached normal operating temperature, feel the heater hoses at the firewall, they should not be the same temperature as the upper radiator hose! They should be notably cooler, if they are the same temperature= bad dual coolant control valve.