Ford Repair: Heater controls, mercury sable, ford taurus

Question
Hi Dennis,
My friend has 1999 Mercury Sable LS, Which I'm told is the same as a Ford Taurus. Her heater doesn't work, fan comes on, A/c works,but there's no heat. I checked all the fuses, but can't find one for the heater. But since the fan works i don't think it is a fuse. She needs help
Thanks

Answer
The most likely problem is in the blend door or the blend door motor. Blend door is the device that mixes the hot and cold air to provide the temp selected by the driver.

One other possibilty is a plugged heater core not allowing the hot coolant thru.