Jeep Repair: 99 wrangler sport NO HEAT!, wrangler sport, heater core

Question
MY 99 wrangler 4.0 has a/c but no heat.  the blower motor is fine the heater core is flowing. I need to know if there is a door inside the heater housing that could be stuck closed, keeping the hot air from circulating? Could there be a short in the temperature selector? Any advise would be wonderful.

Answer
there is a little motor under the dash that mixes the hot and cold air  the doors like to snap and fall down  I did one this weekend. U can look under the dash at the motor and move the temp control back and forth and u will see the motor moving and if it keeps going around  yeah u have a broken door inside the dash.