If I may, I don't think Ford taurus are equiped with a heater control valve (but I may be wrong).
If your heater blows cold air, check your level of coolant, your thermostat, your heater core (possibly plugged), and your blend door (broken blend door common on 1996-up taurus).
If both heater core hoses are hot with heater on and car at normal operating temperature, you know for sure that whether or not there is a control valve, the coolant is going thru the core anyway (therefore it's not the problem).
Now if one of the hoses is cold or lukewarm, I'd say your problem is likely a clogged heater core.
If your car takes a long time to warm up in the morning, or never reaches normal operating temperature, replace the thermostat.
Also, I heard stories of people fixing their heat problem with their Taurus by simply flushing the entire cooling system. If you never serviced the cooling system in your car, now would be a good time.
Finally, it is also possible that your water pump is getting weak, or has a broken impeller or something.
Hope this help
Thursday, January 8th, 2009 AT 2:10 PM