check the heater controls. My previous control face would not move the electric assymbly to really turn on the heat, it was partially on. That also prevented me from getting any heat through the face vents, though you could feel heat through the defrost vent and floor vents, but it was only mild heat. Hence my confusion thinking that a higher thermostat was the answer.
I was going to just swap heater control units, but didn't have the patience to disconect the wiring, and realized i could swap half of the unit and that actually fixed my problem.
One way to check is to look up at the motors under the dash and play with the controls and make sure everything is moving properly. Also make sure you are getting good electrical connections to the unit.