InNeedOfBoost

ok, i have an 88 that i just picked up. a/c blows ICE cold but the heater is a bit iffy. it works fine when i 1st start the car and for the 1st few minutes im dirving. after that, it just goes to cold air. dunno why. after the car sits for a few hours, it works fine again.

any suggestions? i just flushed the coolant yesterday and i dont smell and coolant or anything inside the car, so i dont think the heater core broke.