heater not heating

earlier this evening the heater in my 99 ford taurus would not blow hot air. I tried the vent and all the defrost options but couldn't get anything but cold air. does anyone know what could be the cause?

thanks
tiatibby

Clogged heater core.

Check under the hood behind the engine to see if the hoses to/from the heater core are hot. The hoses are attached to the heater core at the firewall and are spaced approximately 4-5 inches apart. If the hoses do not get hot, the problem might be a clogged heater core, which is an expensive item to have repalced because it entails removing the dash and the book calls for 12 hours. Try removing the hoses to the core and flushing it out with water in both directions, first against the normal direction of flow. If the hoses do not get hot after all has been flushed out with good flow, then your problem is probably the water pump vanes are so eroded away that the pump will not move the water sufficiently to get it through the heater core. If the hoses are hot, check the blend door actuator operation and make sure that you see the linkage on the blend door moving. It also helps to remove the actuator (4 screws) and make sure that the blend door hasn't broken off of the actuator linkage. Hope this helps!

Unless you've recently flushed the coolant system (and inadvertently blocked your heater core with crud), the most likely reason for sudden failure of the heat would be your blend door - probably the actuator. The actuator is controlled by the temp knob on the dash. Lean underneath the dash and look for the linkage that moves the blend door. On my '97, it's a metal "banana" bracket with a slotted hole. If you push upward on this bracket from the bottom as far as it will go, you've got the door in the "full heat" position. If you do this and you get heat, the problem is either the actuator (the little plastic box with a plug externally bolted to the air box), or the innards of the air box itself. You MIGHT have to remove the actuator to freely move the bracket, I don't remember. Right now, my actuator is out and I have the bracket propped up with a piece of 1" plastic inserted into the bracket's slot. This keeps the door in the full-heat position.