No heat

Thermostat is operating properly, heater core/cooling system has been flushed, blower motor control module/resistor (located under the hood next to the blower motor) has been replaced, antifreeze is at the proper level, no leaks, and still no heat. The heat/AC operating controls go haywire at times, where it switches back and forth with absolutely no rhyme or reason. I have torn the dash apart looking for electrical issues/bad grounds, etc. I am out of ideas, I was going to try to pull fuses tonight to see if that helps, but I am not very optimistic about it. Please help if you have any ideas.