EBSCO Auto Repair Reference Center 1991–92 R/V AND 1991–98 C/K SERIES Disconnect the negative battery cable. Drain the cooling system. Remove the instrument panel glove compartment. Tag and unplug all electrical leads as necessary. Remove the center air distribution duct from the floor. If necessary, remove the ECM and mounting tray. Remove the hinge pillar trim panels. Remove the blower motor cover and then remove the motor. Remove the steering wheel and tilt back the instrument panel slightly. Remove the coolant overflow tank. Disengage the heater hoses at the core connections. Unfasten the attaching screws and nut and then remove the heater case. Remove the seven screws and lift off the heater case cover. Remove the fasteners and brackets that hold the heater core to the case and lift the core from the case. To install: Install the heater core in the case. Install the heater case bottom plate. Make sure there is a good seal. Install the heater case into the truck. Tighten the 4 lower screws to 17 inch lbs. (2 Nm); the upper screw to 97 inch lbs. (11 Nm); and the nuts to 25 inch lbs. (2.8 Nm). Connect the heater hoses at the core tubes. Install the coolant overflow tank. Install the instrument panel and the steering wheel. Install the blower motor and cover. Install the trim panels and if removed, the ECM. Install the air distribution duct and reconnect all electrical leads. Install the glove compartment. Fill the cooling system and connect the battery cable. Rear 1992–98 MODELS Disconnect the negative battery cable and drain the engine coolant. Remove the right rear quarter panel trim and then remove the panel itself. Remove the right rear wheelhousing liner. Disconnect the heater hoses from the core. Unplug the electrical lead. Remove the drain valve. Remove the heater module. If necessary, remove the blower motor. Remove the heater case cover. Remove the heater case cover and then remove the heater core. To install: Install the heater core and then install the heater case cover. If removed, install the blower motor. Remove the heater module. Attach the electrical lead. Install the drain valve. Connect the heater hoses to the core. Install the right rear wheelhousing liner. Install the right rear quarter panel and then install the trim. Connect the negative battery cable and fill the engine with coolant. EBSCO Auto Repair Reference Center