I have a 95 Taurus 3.0. Going crazy with the heater. I have changed the waterpump, thermostat, sensors and switches,flushed my system, including heater core. When started, the car will warm up as normal, and heat will blow beautifully. When i start driving, the temperature guage goes down and the heater blows out cool air. I dont know what to do... Only when I start driving does this problem happen. I even changed the waterpump twice. The blender door operates perfectly. I am going nuts. Can anyone help me please!!! Email me any thoughts or tips to SCHNTZR3@aol.com...Thank you
Mike

The symptom you have described is dead-on typical for a stuck open coolant thermostat.

What temp thermostat are you using?