How do you remove the dash?

I would try opening it up (ductwork) where ever you can and blow it out with high pressure air hose, maybe use vacuum sweeper.

go under right side dash and look for an acsees panel on the evaporator case with one screw in it 5.5 mm remove your clogged clean air filter if that doesnt fix it the evaporator core is clogged with dirt and debrie.but the clean air fitler should fix your problem

Here are the instructions with a diagram. If you need to enlarge the diagram save it to your picture files and then enlarge it there.

1. Disconnect battery ground cable, then drain cooling system. See: Engine, Cooling and Exhaust\Cooling System\Service and Repair

2. Disconnect heater hoses from heater core. Plug heater hoses and core fittings to prevent coolant spillage.

3. Remove bolt located below windshield wiper motor, attaching left end of plenum to dash panel.

4. Remove nut attaching upper left corner of evaporator or heater case to dash panel.
5. Disconnect vacuum control system supply hose from vacuum source, then push grommet and hose into passenger compartment.

6. Remove all instrument panel retaining screws and pull instrument panel back as far as possible without disconnecting any wire harnesses.
7. Loosen right door sill plate and remove side cowl trim panel.

8. Disengage temperature control cable housing from bracket on top of plenum. Disconnect cable from temperature blend door crank arm.

9. On models w/Automatic Temperature Control (ATC) , remove cross body brace and disconnect wiring harness from temperature blend door actuator and disconnect ATC sensor tube from evaporator case connector.
10. Disconnect vacuum harness at vacuum connector near floor air distribution duct.

11. Disconnect white vacuum hose from outside recirculating air door vacuum motor.
12. Remove two hush panels.

13. Remove one plastic push fastener retaining floor air distribution duct to left end of plenum. Remove left screw and loosen right screw on rear face of plenum. Remove floor air distribution duct.

14. Remove two screws from rear side of floor air distribution duct to plenum. To remove right screw, it may be necessary to remove the two screws attaching lower panel door vacuum motor to mounting bracket.

15. Remove push fastener attaching floor air distribution duct to left end of plenum, then remove floor air distribution duct.
16. Remove two nuts located along lower flange of plenum.
17. Carefully move plenum rearward, so that heater core tubes and plenum case upper stud clear openings in dash panel, then remove plenum from vehicle by rotating upper portion of the plenum forward, down and out from under instrument panel. It may be necessary to carefully pull lower edge of instrument panel rearward while plenum is being removed from behind instrument panel.
18. Remove retaining screws from heater core cover, then the cover from plenum assembly.

19. Remove retaining screw from heater core inlet and outlet tube bracket.

Heater core removal and installation diagram.






20. Pull heater core and seal assembly from plenum assembly.
21. Reverse procedure to install.

Section 12-03: Air Conditioning System 1992 Town Car/Crown Victoria/Grand Marquis Workshop Manual REMOVAL AND INSTALLATION Plenum Removal

1. Disconnect battery ground cable.

1. Disconnect the heater hoses from the heater core tubes. Plug the ends of the heater hoses to prevent coolant loss.

1. Plug heater core tubes securely to prevent coolant leakage from heater core during plenum removal.

1. Remove three nuts located below the windshield wiper motor retaining the LH end of the plenum to the dash panel (Fig. 15).

FIG. 15 Plenum and Air Inlet Duct Removal

1. Remove one nut retaining the upper LH corner of the evaporator case to the dash panel.

1. Remove LH and RH lower instrument panel insulators.

1. Disconnect two vacuum supply hoses from vacuum source. Push grommet and vacuum supply hose into passenger compartment.

1. Remove all instrument panel retaining screws and pull the instrument panel back as far as possible without disconnecting any wire harnesses.

1. Loosen the RH door sill plate and remove the RH side cowl trim panel.

1. On manual systems, disengage the temperature control cable housing from the bracket on top of the plenum. Disconnect the cable from the temperature blend door crank arm. On ATC systems, remove cross body brace and disconnect wiring harness from temperature blend door actuator and disconnect the ATC sensor tube from the evaporator case connector.
   

1. Disconnect the vacuum jumper harness at the multiple vacuum connector near the floor air distribution duct.

1. Disconnect the white vacuum hose from the outside-recirculating door vacuum motor.

1. Remove two hush panels.

1. Remove one plastic push fastener retaining the floor air distribution duct to the LH end of the plenum. Remove LH screw and loosen RH screw on the rear face of the plenum (Fig. 14), and remove the floor air distribution duct.

1. Remove two nuts from the two studs along the lower flange of the plenum.

1. Carefully move plenum rearward to allow heater core tubes and the stud at the top of the plenum to clear holes in the dash panel. Remove plenum from vehicle by rotating the top of the plenum forward, down and out from under the instrument panel. Carefully pull lower edge of instrument panel rearward as necessary while rolling the plenum from behind the instrument panel.

Installation

1. Route the vacuum supply hose through the dash panel and seat the grommet in the opening.

1. 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.

1. Install three nuts on the studs along the lower flange and one on the upper flange of the plenum (Fig. 15).

1. Install three nuts below the windshield wiper motor to attach the LH end of the plenum to the dash panel.

1. Install one nut to retain the upper LH corner of the evaporator case to the dash panel.

1. Position floor air distribution duct on plenum. Install two screws and plastic push fastener.

1. If removed, position panel door vacuum motor to the mounting bracket. Install two retaining screws.

1. Connect the white vacuum hose to the outside-recirculating door vacuum motor.

1. Connect the vacuum jumper harness to the plenum harness at the multiple vacuum connector near the floor air distribution duct. Install floor duct.

1. Connect the ATC sensor tube to the evaporator case connector on ATC equipped vehicles.

1. Install the cross body brace and connect wiring harness to the blend door actuator on ATC equipped vehicles.

1. 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 as outlined under Adjustments.

1. Install the bolt to attach the lower RH end of the instrument panel to the side cowl.

1. Install the RH side cowl trim panel and tighten the RH door sill plate retaining screws.

1. Install glove compartment door and check arms.

1. Connect vacuum supply hose to vacuum supply.

1. Install RH and LH lower instrument panel insulators.

1. Install two hush panels.

1. Unplug the heater core tubes and connect the heater hoses to the heater core tubes.

1. Fill the cooling system with coolant to replace coolant lost during removal of the plenum.

1. Connect the battery ground cable. Check the system for proper operation.

Heater core is located within the air ducting under dash. It is not the easiest thing to get to. To replace it you will have to remove the centre console and the lower half of the dash panels to get access to the air ducts. You will then have to disconnect the heater hoses on the engine side of the firewall and then remove the ducting from the side of the heater box to get to the heater core.

Removal & Installation

1. Remove the floor air outlet duct extension from the floor duct.
   
2. Remove the center console, if equipped.
   
3. Remove the screws from the center console duct, if equipped.
   
4. Remove the center console duct, if equipped.
   
5. Disconnect the electrical connection at the mode actuator.
   
6. Remove the mode actuator mounting screws from the HVAC module.
   
7. Remove the mode actuator as an assembly with the actuator cam.
   

Mode actuator location

To install:

1. Install the mode actuator as an assembly with the actuator cam.
   
2. Line up the heater/defroster valve lever with the mode actuator cam slot.
   
3. Line up the A/C valve lever with the mode actuator cam.
   
4. Install the mode actuator mounting screw to the HVAC module and tighten to 14 inch lbs. (1.6 Nm).
   
5. Connect the electrical connection at the mode actuator.
   
6. Install the center console duct, if equipped.
   
7. Install the screws to the center console duct, if equipped, and tighten to 14 inch lbs. (1.6 Nm).
   
8. Install the center console, if equipped.
   
9. Install the floor air outlet duct extension to the floor air duct.
   
10. Calibrate the HVAC module actuators.
    

big job, dificulty 8 on a 10 scale Heater Air Plenum Chamber Removal

1. Remove heater outlet floor duct (18C433) as described.
   

1. Remove instrument panel (04320). Refer to Section 01-12 .
   

Instrument Panel SPECIAL SERVICE TOOL(S) REQUIRED Description Tool Number Radio Removing Tool 415-001 (T87P-19061-A)
Removal and Installation

1. Disconnect battery ground cable (14301).
   

1. Remove RF wheel and tire assembly. Refer to Section 04-04 .
   

1. Remove three nuts in radiator coolant recovery reservoir area.
   

1. Remove bolt retaining front fender apron (16054) to front fender (16005) .
   

1. Position front fender splash shield out of the way.
   

1. Lower vehicle.
   

1. Tag and remove main harness connector from jumper harness (located in front of blower motor).
   

1. Remove steering column. Refer to Section 11-04 .
   

1. Remove RH cowl side trim panel (02344) and LH cowl side trim panels (02345) .
   

1. Tag and disconnect wiring connectors in LH and RH cowls.
   

1. Remove ground wire located on LH cowl side.
   

1. Remove RH instrument panel upper moulding (04268) and LHinstrument panel moulding (04389) from instrument panel (04320) by pulling away from instrument panel and snapping out of retainers. Disconnect wiring connectors as required.
   

1. Remove glove compartment (06010).
   

1. Remove instrument panel upper finish panel (044A90) and disconnect the A/C sunload sensor (19E663) and anti-theft indicator, if equipped.
   

1. Disconnect the heater water hoses (18472) from the heater core tubes. Plug the ends of the heater water hoses to prevent coolant loss.
   

1. Plug heater core tubes securely to prevent coolant leakage from heater core (18476).
   

1. Remove one nut retaining the upper LH corner of the A/C evaporator core housing (19A559) to the dash panel (01610) .
   

1. Disconnect two vacuum supply hoses from vacuum source. Push grommet and vacuum supply hose into passenger compartment.
   

1. Disconnect wiring harness from A/C electronic blend door actuator.
   

1. Disconnect the white vacuum hose from the heater and A/C air inlet duct door vacuum control motor (18A318).
   

1. Remove nuts from the studs along the lower flange of the heater air plenum chamber (18471).
   

1. Disconnect connectors to A/C electronic blend door actuator and electronic module on side of heater air plenum chamber.
   

1. Remove heater air plenum chamber by pulling rearward.
   

Heater Air Plenum Chamber and Air Inlet Duct





Item Part Number Description 1 19C836 Suction Accumulator/Drier 2 56956-S2 Screw (2 Req'd) 3 386877-S36 Screw 4 45445-S36 Nut and Washer Assy 5 19C928 A/C Recirculating Air Duct Screen 6 386877-S36M Screw (2 Req'd) 7 45332-S12 Nut and Washer 8 19B762 A/C Air Inlet Door Inner Seal 9 19C590 A/C Recirculating Air Duct 10 18471 Heater Air Plenum Chamber 11 18C433 Heater Outlet Floor Duct 12 55734-S2 Nut 13 19A559 A/C Evaporator Core Housing 14 45332-S2 Nut and Washer A — Tighten to 2.5-3.2 Nm (23-28 Lb-In)
Installation

1. Route the vacuum supply hose through the dash panel and seat the grommet in the opening.
   

1. Position the heater air plenum chamber under the instrument panel with the A/C register duct opening up and the heater core tubes down. Connect wire harness connector to A/C electronic blend door actuator and electronic module on side of heater air plenum chamber .
   

1. Rotate the heater air plenum chamber up behind the instrument panel and position the heater air plenum chamber to the dash panel. Insert the heater core tubes and mounting studs through their respective holes in the dash panel and the A/C evaporator core housing.
   

1. Install three nuts on the studs along the lower flange and one on the upper flange of the heater air plenum chamber.
   

1. Install three nuts below the windshield wiper motor (17508) to retain the LH end of the heater air plenum chamber to the dash panel.
   

1. Install one nut to retain the upper LH corner of the A/C evaporator core housing to the dash panel .
   

1. Connect the white vacuum hose to the heater and A/C air inlet duct door vacuum control motor.
   

1. Connect the vacuum jumper harness to the plenum harness at the multiple vacuum connector near the heater outlet floor duct. Install heater outlet floor duct.
   

1. Connect the sensor tube to the evaporator case connector on EATC-equipped vehicles.
   

1. Connect vacuum supply hose to vacuum supply.
   

1. Unplug the heater core tubes and connect the heater water hoses to the heater core tubes.
   

1. Fill the cooling system with coolant to replace coolant lost during removal of the heater air plenum chamber.
   

1. Install heater outlet floor duct as described.
   

1. Install instrument panel. Refer to Section 01-12 .
   

Section 12-03A: Air Conditioning System—Manual A/C-Heater 1998 Crown Victoria, Grand Marquis Workshop Manual
REMOVAL AND INSTALLATION Heater Core Removal
NOTE: If a heater core leak is suspected, the heater core must be pressure leak tested before it is removed from the vehicle. Refer to Section 12-00 .

1. Remove the heater air plenum chamber (18471) assembly as described.
   

1. Remove the heater dash gasket (18570) from the heater air plenum assembly.
   

1. Remove the four retaining screws from the heater core cover (18B300) and remove the heater core cover from the heater air plenum chamber assembly.
   

1981-87 Models

1. Disconnect battery ground cable.
2. Discharge A/C system and disconnect refrigerant and heater lines from unit.
3. Move shift levers away from dash.
4. Remove right side cowl trim panel, if equipped.
5. Remove 4 screws at base and remove glove box.
6. Remove brace through glove box opening and remove ashtray.
7. Remove right half of lower reinforcement (7 screws to instrument panel and 1 to cowl side of trim panel).
8. Disconnect radio ground strap.
9. Remove right upper air duct by removing mounting screw and pulling duct out through glove box opening.
10. Remove instrument panel center brace and right instrument panel cluster pivot bolt.
11. Remove instrument panel cluster, disconnect shift indicator cable and lower steering column.
12. Remove steering column studs and radio.
13. Remove scoop connecting heater to center distribution duct (2 screws).
14. Remove center distribution duct by pulling bottom of dash out to gain clearance.
15. Remove floor air distribution duct.
16. Disconnect temperature control cable through glove box.
17. Remove 7 retaining nuts from firewall and screw that retains assembly to cowl side sheet metal.
18. Flex dash out and remove heater assembly.
19. Remove nuts from door arms and remove door arms.
20. Remove 7 screws to remove cover from housing.
21. Remove evaporator core.
22. Reverse procedure to install.

one of 2 problems either the air ducts have come loose or have tears in then remove dash panel check air duct hoses while running feel for air or vaccumm lines are miss routed

clogged airconditioning system. have it cleaned.

happened to me too, only, it is under the passenger side's dash.

hope it helps.