I have a 1994 Dodge 2500 with the V-10, the engine heats up but the heating syst on 1994 Dodge Ram 2500

I have flushed the coolant system and replaced the thermostat, yet the problem still exists. I am at a loss right now. The heat controls seem to work ok, like switchijng from dash heat to floor and windshield, only there is no heat.
Thanks in advance for any suggestions or advice.

Asked by for the 1994 Dodge Ram 2500
poss fan clutch is needed a simple test start trk watch fan clutch while someone turns off eng. the fan clutch should stop turning in about 5 seconds if it goes longer its BAD
The fan clutch is fine, all the heater hoses and radiator hoses get hot, but no hot air in the cab. Like I mentioned in my question, I did flush the entire system.
sorry read it wrong. is heater core plugged or bad heater control valve