GM 91174886 Core,Heater

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On vehicles with air conditioning, have the air conditioning system discharged by a dealer service department or an automotive air conditioning shop. For vehicles with airbags, disable the airbag system. Drain the cooling system. Working in the engine compartment, disconnect the heater hoses where they enter the firewall by loosening the hose clamps, sliding them back, and pulling off the hoses. Remove the instrument panel and, if equipped, the center console. If the vehicle has air conditioning, remove the evaporator unit. Label and detach the air ducts, wiring, and controls still attached to the heater housing. On 1999 and later models, remove the air conditioning controller if equipped, and for vehicles with airbags, remove the Sensing and Diagnostic Module. Unbolt the heater housing unit and lift it from the vehicle. Remove any remaining heater core pipe clamps and then take out the rubber grommet where the two heater core pipes protrude through the firewall. Remove the screws or clips that secure the two halves of the heater housing, then separate the two halves and take out the old heater core to install the new unit. Reassemble the heater housing unit and check the operation of the air control flaps, correcting any binding issues before installation. Reinstall the remaining parts in the reverse order of removal. Refill the cooling system, reconnect the battery, and run the engine, checking for leaks and proper system operation.