GMC 84406079 Heater Core

To remove the front heater core, start by disconnecting the cable from the negative battery terminal and draining the cooling system. Remove the driver's seat and the driver's side floor console extension panel. Then, remove the floor outlet duct and the heater core cover. Disconnect the heater core tubes and carefully pull out the heater core from the heater case. For installation, follow the reverse steps and refill the cooling system with the proper antifreeze concentration. Start the engine and check for any leaks. To remove the rear auxiliary heater core, first have the air conditioning system recovered. Loosen the right-rear wheel lug nuts and raise the rear of the vehicle on jackstands. Remove the right rear wheel and inner fender splash shield. From below the vehicle, disconnect the heater hoses and refrigerant lines from the rear auxiliary HVAC module fittings. Remove the HVAC module mounting nut. Inside the vehicle, remove the rear storage compartment, third-row seat, and passenger's side rear quarter trim panel. Disconnect the electrical connector for the rear auxiliary HVAC unit. Remove the air conditioning air outlet duct and the heater air outlet duct. Remove the module mounting bolts and remove the module from the vehicle. Place the module on a flat surface and remove the rear auxiliary evaporator tube clips. Remove the HVAC module lower cover bolts and the cover. From the front of the module, remove the HVAC module case screws and separate the case halves to access the heater core. Carefully pull out the heater core from the HVAC case. For installation, follow the reverse steps and refill the cooling system. Finally, have the system evacuated, recharged, and leak tested.