Drain the cooling system and disconnect the heater hoses from the heater core tubes. Plug the hoses and the heater core tubes to prevent coolant leakage.
Remove the 3 nuts located below the windshield wiper motor attaching the left end of the plenum to the dash panel. Remove the 1 nut retaining the upper left corner of the evaporator case to the dash panel.
Disconnect the vacuum supply hose(s) from the vacuum source. Push the grommet and vacuum supply hose(s) into the passenger compartment.
Remove the right and left lower instrument panel insulators.
On 1990-00 vehicles:
Remove the cross body brace and disconnect the wiring harness from the temperature blend door actuator.
Disconnect the ATC sensor tube from the evaporator case connector.
Disconnect the vacuum jumper harness at the multiple vacuum connector near the floor air distribution duct. Disconnect the white vacuum hose from the outside-recirculating door vacuum motor.
Remove the 2 hush panels.
Remove 1 plastic push fastener retaining the floor air distribution duct to the left end of the plenum. Remove the left screw and loosen the right screw on the rear face of the plenum and remove the floor air distribution duct.
Remove the 2 nuts from the 2 studs along the lower flange of the plenum.
Carefully move the plenum rearward to allow the heater core tubes and the stud at the top of the plenum to clear the holes in the dash panel. Remove the plenum from the vehicle by rotating the top of the plenum forward, down and out from under the instrument panel. Carefully pull the lower edge of the instrument panel rearward, as necessary, while rolling the plenum from behind the instrument panel.
Remove the 4 retaining screws from the heater core cover and remove the cover from the plenum assembly. Pull the heater core and seal assembly from the plenum assembly.
Carefully install the heater core and seal assembly into the plenum assembly. Visually check to ensure that the core seal is properly positioned. Position the heater core cover and install the 4 retaining screws.
Route the vacuum supply hose through the dash panel and seat the grommet in the opening.
Position the plenum under the instrument panel with the register duct opening up and the heater core tubes down. Rotate the plenum up behind the instrument panel and position the plenum to the dash panel. Insert the heater core tubes and mounting studs through their respective holes in the dash panel and the evaporator case.
Install the 3 nuts on the studs along the lower flange and one on the upper flange of the plenum. Install the 3 nuts below the windshield wiper motor to attach the left end of the plenum to the dash panel and the one nut to retain the upper left corner of the evaporator case to the dash panel.
Position the floor air distribution duct on the plenum. Install the 2 screws and plastic push fastener. If removed, position the panel door vacuum motor to the mounting bracket and install the 2 attaching screws.
Connect the white vacuum hose to the outside-recirculating door vacuum motor. Connect the vacuum jumper harness to the plenum harness at the multiple vacuum connector near the floor air distribution duct. Install the floor duct.
If equipped with manual air conditioning, connect the temperature control cable housing to the bracket on top of the plenum and connect the temperature control cable to the temperature blend door crank arm. Adjust the temperature cable.
If equipped with ATC, proceed as follows:
Connect the temperature control cable to the ATC sensor and adjust the cable. Route and connect the vacuum harness connector to the ATC sensor and connect the electrical connector to the ATC servo connector. Do not block the sensor aspirator exhaust port with the excess vacuum harness. Install the ATC sensor tube between the sensor and the evaporator connector.
Connect the ATC sensor tube to the evaporator case connector.
Install the cross body brace and connect the wiring harness to the blend door actuator.
Install the bolt to attach the lower right end of the instrument panel to the side cowl. Install the right side cowl trim panel and tighten the right door sill plate attaching screws.
Connect the vacuum supply hose(s) to the vacuum source.
Install the right and left lower instrument panel insulators and install the 2 hush panels.
Unplug the heater core tubes and the heater hoses and connect the heater hoses to the heater core tubes. Fill the cooling system.
Connect the negative battery cable and check the system for proper operation. I hope this helps. Don,t forget to rate my answer.
I have the same problem in my 2001 towncar. I removed the switch control panel (without removing the door panel) by prying up from the front of the panel. There's a spring loaded plug under the mirror adjustment. Once you get that pulled up, the whole unit will lift out. Since there's a two year difference in the models - it MAY not work... however, you might not have to remove the whole door panel as you think.
In my case, the wiring was bad.
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The first thing that comes to mind is a possible leaking heater core. If this is the case, the procedure to replace it is quit labor intensive.I have a question though, what temperature is it that is not getting hot? Is it the engine, or the temp of the heater?
Hi John,A heater core replacement is a very fragile and difficult job, I strongly suggest that you have a shop do this job. It is really easy to damage hard to get pieces, as well as the core itself....
That is about a 9 hour job. The heater core in in the Heater Air plenum chamber which is behind the dash. the dash has to be removed to replace the heater core. It is an involved job. Lots of bolts, screws wireing connectord and vacume connectors to remove and un plug. Some are behind the inner fender splash guard. The book wants you to remove the complete Heater Air Plenum, But it can be done with Patience and finess.