2007 Express 3500 4.8 No Heat

I have no heat coming out of my vents. I replaced the thermostat, flushed the system, made sure it was bled properly and still no heat. The temp gauge reads between about two-three lines below 210 degrees and there is no check engine light. What else could be causing this.

I have no heat coming out of my vents. I replaced the thermostat, flushed the system, made sure it was bled properly and still no heat. The temp gauge reads between about two-three lines below 210 degrees and there is no check engine light. What else could be causing this.

Feel heater hoses if not hot to the touch the heater core is plugged.
If hot then the vent or mode doors or controls are bad or not getting engine vacumn.
Check fuses and vacumn to controls.

Automatic or manual controls?