my car blows cold air from the heater...why

most times its the thermostat, next its cloged heater core,or deverter flaps not moving under dash.try blocking 1/2 rad. front with cardboard, if some heat appears its thermostat

If that doesn't do it see if the valve that opens the flow to the heater core opens, the valve or linkage to it may be stuck

I just now noticed that it's a '99 Taurus. For that one year, '99 only, Ford put a bypass around the heater core so that if the heater core were to get plugged the engine would not overheat. I would have to pull up a hose diagram I don't remember exactly why..as if the coolant flowed through the heater core all the time, anyway if the coolant is getting diverted through that bypass there you are, no heat

You say try blocking 1/2 rad on a 1999 Taurus that is not blowing heat what do you meen by that

"Block 1/2 rad" means fasten cardboard (or similar) in front of half the radiator to block airflow. If your engine never heats up because the thermostat is stuck open and coolant flow is over-cooling the engine, blocking the radiator is the cheapest work-around to replacing the thermostat.