i have a 97 deville with the north star i have had the head gaskets changed radiator and heater core blower works good problem i have is it seems to be blowing cold air like from ac instead of heat thermastat is good temp gage stays within range 217 to 221 degrees i need some suggestions before just replacing things

 

Make sure coolant is full. If both heater hoses are hot...not warm .....HOT!..If they are remove glove box and check operation of programmer arm. Arm actuates hot/cold door. It should move as temp is cycled from 60 to 90 on control head. If hoses aren't hot there is a restriction or low coolant level. If you can remove heater hoses from heater core make sure coolant is getting there. You could use garden hose and reverse flush core see it corrects condition. NOTE: this is an old car. Heater core tubes are plastic it is possible to BREAK them with little effort. If this is your daily driver you might want a back up plan before trying to remove hoses.