GM 15781482 Core Assembly, Heater

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To remove the heater core, start by disconnecting the cable from the negative battery terminal and draining the cooling system. Then, disconnect the heater hoses from the heater core pipes at the firewall and plug the pipes to prevent coolant spillage. Remove the entire instrument panel and disconnect the control cable from the shifter. Press the cable clip tabs and release the cable from the shifter. Disconnect all wiring from the shift assembly and unbolt the shifter to gain access to the heater core. Remove the large duct from the front of the heater unit and the heater core cover. Remove the small plastic cover and foam seal from the heater core pipes. Finally, remove the heater core by pulling on the end tank. For the second removal method, have the air conditioning system refrigerant discharged and recovered by a technician. Disconnect the cable from the negative battery terminal and drain the cooling system. Remove the retaining nut for the refrigerant line fittings and disconnect them, plugging all open lines and fittings. Disconnect the heater hoses from the heater core pipes at the firewall and plug the pipes. Remove the heater/air conditioning unit mounting nuts at the firewall and the instrument panel. Detach the control cable from the shifter and disconnect all wiring from the shifter assembly. Remove the four nuts for the shifter assembly and remove the assembly. Remove the defroster, center, and floor air ducts, as well as the steering column and brake pedal assembly. Remove the mounting fasteners for the heater/air conditioning unit and the instrument panel support. Disconnect the electrical connectors for the blower motor and module, as well as all other electrical connectors and wire harnesses. Carefully pull the heater/air conditioning unit away from the firewall and remove the heater core cover. Finally, pull the heater core from the unit. To reinstall, simply reverse the removal steps and refill the cooling system.