Ford Repair: 98 explorer heater, heater settings, vac supply

Question
The temp control on my explorer does not work. Last year ir was noticably noisy and SLOW to change from hot to cold. Various heater settings (def, vent, heat) do not work either. I believe it mat be a vacum modulator for the control from hot to cold. Where is this located and how do I get to it. It is a 98 Ford Explorer 4 door 4.0 v-6. with air.  

Answer
Hello and thanks for the question...I'll try to help.
 I would make sure that the interior is getting a vac supply signal from the engine. In the engine compartment, you should see a vac line (black) going in to the fire wall. Trace this line back to the source and make sure it's not plugged with carbon build up, or a kinked/melted line.
Hope this helps,
Erik