Just replaced thermostat, that did not help. Both hoses attached to the heater core are hot, and coolant level is ok. Fan works fine, and the selector **** is working fine, just no heat at all. Pulled the temp control **** and turned selector with pliers, that seems to be working fine as well. Any ideas?

 

the heater core is probably clogged.

 

So, I drove the truck to pick up the kids earlier, and the heat started to work, although I'm not sure that it is as hot as it should be. Earlier when I posted, the truck had sat and idled for 15-20 minutes, but was not actually driven, and the heat never did get hot. Could it be that there was air trapped in the line, or maybe the water pump isn't pumping like it should?

 

engine would overheat if the water pump was failing.

it is possible to have an air bubble was trapped in the heater core

you can pull the lines off the heater core once everything cools down, and try to flush through both directions on the cooler to make sure its not clogged

 

My heat is now working. Out of curiosity, I checked to see if the A/C is working, and it is not. This leads me to believe that it is the blend door. At least I have heat for the winter, I will tackle that job once it gets warmer out.
Before I do, is there anything else that this could possibly be, anything else that I should check? I would hate to do all of that work, only to find that the problem lies elsewhere.
Also, has anyone ordered the blend door from an aftermarket company? I found one on EBay for $35 and some change, while my local dealership wants $85 for the same thing.