GM Genuine Parts HVAC Heater Cores are designed, engineered, and tested to rigorous standards, and are backed by General Motors. These HVAC heater cores are small radiators, located in the plenum behind the dashboard. Engine coolant flows through the heater core in order to heat the air in the passenger compartment. GM Genuine Parts are the true OE parts installed during the production of or validated by General Motors for GM vehicles. Some GM Genuine Parts may have formerly appeared as ACDelco GM Original Equipment (OE).