E-150 HEAT CONTROL VALVE

I have a 1989 E-150 CONVERSHEN VAN

I hope some one can tell me wheir the heat contol valve

is located, so that I can trurn it back on so that we

have good heat again. My new wife has had the van since it was new, but her x refuses to tell her wheir it is located

and the end result being, we have very little heat as a result.

So I hope some one can help me with this.