If the windshield on your Jeep Grand Cherokee won't properly defrost or the passenger side of the vehicle has a wet floor board, the heater core may be at fault. Heater core removal can be a difficult task for a home mechanic, however, if done in a slow and methodical manner with attention to detail, particularly wiring and fasteners, it can be a successful endeavor. Make sure you allocate enough time for the project in order to avoid rushing, particularly since the entire instrument panel must be removed to access the heater and air conditioning unit.
Discharge the air conditioning system pressure by taking your Jeep to a dealership or service center. The system's fittings are under high pressure, so do not attempt to disconnect the fittings prior to evacuation of the freon.
Disconnect the negative cable from the battery's terminal. Drain the cooling system into a disposal container from the radiator and the engine block drain plugs. Disconnect the heater hoses at the inlet and the outlet of the heater core.
Remove the console, lower the steering column and remove the instrument panel assembly. To remove the console, position the shift lever in the fully rearward position and remove the front and rear storage bins. Then remove the console mounting screws, lift the console upward, disconnect electrical connectors and remove the console. Use the lever on the side of the steering wheel to lower the steering column to its lowest position. To remove the instrument panel assembly, use a trim tool to pry the attachment clips loose to release both the upper and lower panels. Remove the ashtray and disconnect electrical connectors behind each panel.
Disconnect the blower motor electrical connector, which is located under the glove compartment area of the dash near the firewall. Bend back the clip on one of the mounting screws and release the wiring harness. Pull the harness down and disconnect the electrical connector.
Disconnect the air-conditioning lines from the evaporator by unbolting the refrigerant lines from the firewall with a wrench.
Remove the coolant reservoir by loosening the hose clamp and detaching the hose from the reservoir. Disconnect the electrical connector from the coolant level sensor. Remove the screws and lift the reservoir out of the vehicle.
Detach the PCM computer from the firewall, but do not disconnect the 60-pin connector. Pull the PCM far enough away to remove the heater/air conditioning unit attaching nuts from the studs on the engine compartment side of the firewall. There are three nuts behind the computer and one at the center of the firewall.
Label the electrical connectors of the heater/air conditioning unit and the blower motor resistor/control module. Disconnect the electrical connectors. Disconnect the vacuum hose at the vacuum motor. Remove the evaporator drain tube. Remove the defrost duct, locate above the heater/air conditioning unit.
Disconnect the rear floor heating duct from the center adaptor heat duct.
Remove the nuts from the studs on the interior side of the firewall and pull the heater/air conditioning unit from the vehicle.
Remove the retaining screws and remove the heater core from the top of the unit by pulling it straight up and out of the housing.
Position the new heater core into the housing and reinstall the retaining screws. Install the heater core and cement the seal in place to keep it from moving during installation of the blower assembly.
Reinstall the remaining components in reverse order of removal. When reinstalling the coolant tubes to the heater core, install the new O-rings before clamping the tubes to the core. When installing the blower/evaporator housing, avoid pinching the wiring between the housing's air inlet and the instrument panel on the right side of the housing.
Refill the air conditioning coolant system by adding coolant to the radiator and reservoir until full. Start the engine to check for proper operation of the heating system. Do not turn on the air conditioning system until it has been recharged and leak-tested.
