93 Seville NO HEAT

1993 Cadillac Seville 4.9 V8. I currently have no heat in my car. There is plenty of anti-freeze in both the resevior and Radiator. The windshield defroster works faintly, back windshield defroster works fine. Does anyone know how to approach this?

Check to see if the hoses to the heater core are warm. If not, I'd look into a faulty control valve. If you've never done it, a heater core back flush might help if it's a clog that's the problem.