Ford: Heater control valve subject, heater control valve, firwall

Question
Where is the heater control valve located on the truck and what's the best way to get to it.  Couldn't find a diagram online anywhere to look at.  Thx

Answer
I have never seen a heater (water) control valve on a truck unless it was installed later. But if it did have one, it would be in the heater hose to the firwall.  Why are you looking for it?
Sorry, i have been sick and not had a chance to look further into your problem.  What is the year, make a nd model of the truck in question please. and engine code or size.