Took 300+ mile trip last weekend in my 07 and because the morning was a bit cool and damp I turned on the heat along with the a/c as a dehumidifier. I got no heat, at all. With the a/c off, no heat. The temp control switch feels like a simple rheostat so I am thinking this is an electronically controlled water valve. Any help/info would be appreciated. Thanks, Charles

 

Often no heat is due to no coolant in the heater core. That would be bad since it means your coolant is very low, air in the system, and you could overheat motor at any time.

First make sure this is not a coolant issue before you drive car any further.

Assuming that all checks out, does it blow cold ok? What about defroster (with ac off)? Is that blowing warm?

See if recycle cabin air setting makes any difference.

 

Nope water is filled to the top and in the 330 mile trip the engine stayed cool despite it being in the mid-high 80's and me running 70+. I tried all the vent position with and with out the a/c on, no heat in any position you put the temp control or the vent control switch in or in the recycle mode. The valve is just not being opened.
Now I looked in the engine bay but could not find the valve in there, granted it was on Sunday morning before my coffee and I have been too busy to go rooting around since then. Is the valve in the engine bay or inside the cabin??

 

I mentioned earlier about replacing or adding coolant. I wonder if you went through the final stages of Billman's thread and tried to squeeze and vent just to see if somehow air got in there might help.