Heater coil has been replaced as well as heater hoses and radiator fan runs but blows cold air
No heat on S10 pickup on 1991 Chevrolet S10
poss stuck open thermostat. start there
2 more answers
heater control valve broken? Temp door working properly inside?
if you replace the heater core already check the heater core hoses if its get hot or not maybe blocked, maybe just not working/hoses wrong connections, is your temp normal? is your thermostat new?