I have a 1999 taurus, I have no heat. It will get warm when idoling on the vent setting, but when driving have no heat at all. Think maybe heater core but not sure.
heater problem on 1999 Ford Taurus
A quick method to tell if you have coolant flow through the heater core is to feel and compare the temperature of the inlet and outlet heater hoses. A clogged heater core will have only the inlet hot or warm. A stuck open thermostat could also create this concern.