The heater is not heating up. I think the radiator needs to be replaced.
The heater needs for the engine to be warm, and the temperature blend door to open, in order to direct heat to the passenger compartment from the AC side. If the radiator was plugged, then the engine may be overheating. The thermostat may be stuck open, preventing the engine from getting warm enough. I recommend that you have a mechanic, such as one from YourMechanic, do a thorough check of the cooling system and AC heat system.
Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing