How do I get to and change the heater core?

To get to the heater core, you must remove the entire HVAC housing assembly. This is a very involved process. If you've never done this before, I don't recommend doing it. But if you're sure you can handle the job, I suggest you purchase a service manual or a "Single Vehicle" subscription to a service such as AllData or Mitchell 1. This will provide you with detailed illustrations as well as helpful hints/tricks for this and future projects.

Here's the procedure:

REMOVAL

Disconnect battery. This must be done to prevent accidental air bag deployment.
Using an A/C recovery unit, remove all R-134a refrigerant from the A/C system. Refer to: Heating and Air Conditioning, Service and Repair, Refrigerant Recovery, See: Service and Repair Refrigerant Recovery
Remove air cleaner hose and air distribution duct from the engine.
Drain the engine cooling system.
Disconnect heater hoses at the dash panel. Plug the heater core inlet and outlet tubes to prevent anti-freeze from spilling on the vehicle interior during removal. If an appropriate plug cannot be found pull back carpet and use caution when removing unit. Keep the heater tubes elevated to prevent spillage of coolant.
Remove both A/C lines from expansion valve. Use special tool 7193 to disconnect quick connectors on A/C lines. Refer to: Heating Air Conditioning, Hose/Line HVAC, Service and Repair, See: Hose/Line HVAC Service and Repair After removing lines cap the expansion valve openings and the A/C hose openings. This will prevent any dirt or moisture from entering the refrigerant system during servicing. CAUTION: The lubricant used in this air conditioning system absorbs moisture readily (similar to brake fluid). Do not leave any portion of the system open for extended periods of time.
Remove the three retaining nuts from the studs. These studs project through the dash panel into the engine compartment.
Remove right and left instrument panel end caps. These caps are held in place by a series of clips. Refer to
Remove right and left interior door post kick panel.
Trim Cap Removal

Remove right side bezel from instrument panel.
Remove the radio center bezel which is held in place by six clips. This can be done by carefully prying the bezel from the instrument panel.
Remove the radio. Remove the heater A/C control head from the panel and place in a safe area.
Center Bezel Removal

Remove the center instrument panel bezel. This bezel is held in place by four clips. It can be removed by carefully prying it from the instrument panel.
Remove center console from vehicle (if equipped).
If the vehicle is equipped with a right side air bag, the glove box must be lowered. The glove box assembly can be lowered by pressing in on the sides of the glove box. This will release the glove box and allow access to air bag mounting screws. There are four screws located behind the glove box. Remove these screws and then close the glove box.
Remove lower bolster retaining screws.
Carefully lower the bolster and disconnect the trunk release and glove box light wiring. Then remove the lower bolster from the vehicle.
Panel Top Cover

Remove the instrument panel top cover. It is held in place by retainer clips at both ends of the cover. To remove carefully pry upward at one end of the cover until the clip is disengaged. Proceed to the opposite side and gradually pry the rear edge of the top cover along the entire width of the panel.
Remove right and left windshield pillar trim covers.
Remove five bolts that hold instrument panel to the cowl. These bolts are located at the base of the windshield.
Disconnect the scan tool (DRB) connector from brace.
Remove instrument panel ground strap. This strap is located on the lower left side of the center console.
Remove left knee blocker support bracket. This will allow access to the 60 way wiring connector.
Remove under column duct and left floor duct.
Disconnect 60 way wiring connector. Then disconnect all related wiring connectors.
Disconnect fuse panel wiring connectors.
Disconnect the brake light switch connector.
Remove steering column covers from steering column.
Remove steering column retaining bolts and allow the steering column to lower to the floor. Do not completely remove the column from the vehicle.
Remove wiring from the steering column.
Remove air bag connectors.
Remove right side floor air duct.
Disconnect 10 way connector, blower module connector and blower motor connector.
Remove body controller from vehicle.
Disconnect right side connector and antenna connector.
Remove right and left side upper instrument panel mounting screws located in door jam.
Remove upper instrument panel from the vehicle. The upper instrument panel will be removed with all harnesses and gauges still in the panel. It is recommended that two people handle the upper panel while removing.
Remove air duct for rear heater vents. It is held in place by a bracket/push pin near the rear of the duct.
Remove the air bag module and brace from the vehicle.
Remove three attaching bolts which holds the heater housing to the dash panel.
Carefully roll the heater housing out of the vehicle.
After removing the heater housing, remove the drain tube from the heater housing. The drain tube should be installed from underneath the vehicle after the heater housing is reinstalled into the vehicle.

After removing the housing, you can easily remove the heater core.

INSTALLATION

For installation, reverse the above procedures.