Heater not working 99 Tauraus

WE just reciebed a 199 ford taturas in Aug.Everything works great on it. What would cause th air to blow just cold air, sns sometimes it bloed out hot air. The gauges look ok with water temp so i know the the therostat is workiing. If anyone could help it would be great thanks

Spell check would make your post easier to read.
Clogged heater core.
Malfunctioning blend door.
Low coolant level.
Vacuum leak under the dash affecting the heater controls.
Heater controls.
Thermostat stuck open.
Bad waterpump.
Could you please clarify your meaning about "hot air"

I also own a 1999 Taurus SE. I have talked with the dealers on these problems before and they say that the 3.0 Vulcan engine has a internal rust issue. It needs to be flushed regularly but in the case of your problem, cold air, it probably means your Heater core is clogged up. You can purchase a Preston Flush kit to flush the system but this still won't unplug your heater core due to the way the hoses bypass the core. Your best bet is to take a garden hose, cut the end and clamp it onto one side of the heater core and directly flush it. If it is plugged, you will probably see rust clogged once you remove the heater hose. If you have to replace the heater core, have fun... You must remove the dash, drop steering wheel, cluster etc. to get enough clearance to remove the heater core. It is not hard, just time consuming. It took me around 3.5 hours start to finish at home.