93 Aerostar front heater does not work?

My earostar front heater does not put out any heat. I have checked the heater hoses that go to the heater core and one was hot and one was cold. I took one hose off and flushed the heater core with a garden hose. Water was flowing throught the heater core. I put crdboard in front of the radiator to see if the thermostat might be the problem but still no heat. I have also check the operation of the doors inside that control air flow and they seem to be working fine. The water pump is new and the thermostat is new. Don't know what else could be wrong.