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Eric
Eric, Automotive Repair Shop Manager
Category: Jeep
Satisfied Customers: 29970
Experience:  20+ yrs. experience as repair shop manager and technician.
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Jeep how do I replace the heater core in a 99 cherokee

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how do I replace the heater core in a 99 cherokee
Hi,

below are directions to remove the dash and replace the heater core:

  1. Disconnect and remove the negative battery.
    CAUTION
    After disconnecting the negative battery cable, wait 2 minutes for the driver-s/passenger-s air bag system capacitor to discharge before attempting to do any work around the steering column or instrument.

  2. Drain the cooling system into a clean container for reuse.
  3. Remove the instrument panel by performing the following procedure:
    1. Turn the steering wheel in the straight-ahead position.
    2. Remove the knee blocker from the instrument panel.
    3. Remove the steering column; do not remove the air bag module, the steering wheel or switches from the steering column.
    4. From under the driver-s side of the instrument panel, disconnect the following items:

      Instrument panel wiring harness connector from the 100-way wiring harness connector at the left side of the inner panel.
      Side window demister hose at the heater/air conditioning housing demister/defroster duct on the driver-s side.

    5. Remove the glove box.
    6. Reaching through the glove box opening, disconnect the following items:

      Two halves of the heater/air conditioning system vacuum harness connector.
      Instrument panel wiring harness connector from the heater/air conditioning system wiring harness connector.
      Instrument panel wiring harness connector from the passenger-s side air bag module wiring harness connector.
      Side window demister hose at the heater/air conditioning housing demister/defroster duct (passenger-s side).
      Two halves of the radio antenna coaxial cable connector.
      Two instrument panel wiring harness connectors from the passenger air bag ON/OFF switch wiring harness connector.
      Passenger-s side air bag ON/OFF switch wiring harness from the retainer clip on the plenum bracket that supports the heater/air conditioning housing just inboard of the fuse block module.
      Two lower passenger-s side air bag module bracket-to-dash panel nuts.

    7. Remove the upper cover from the instrument panel.
    8. Remove the 3 instrument panel-to-door hinge pillar screws.
    9. Remove the 4 upper instrument panel-to-dash nuts.
    10. Using an assistant, remove the instrument panel from the vehicle.

  4. If equipped with air conditioning, discharge and recover the air conditioning system refrigerant.
  5. Disconnect the refrigerant lines from the evaporator. Plug the refrigerant openings to prevent evaporation.
  6. Disconnect the heater hoses from the heater core tubes.
  7. Disconnect the heater/air conditioning system vacuum supply line connector from the T-fitting near the heater core tubes.
  8. In the engine compartment, remove the 5 heater/air conditioning housing-to-chassis nuts. If necessary, loosen the battery hold-downs and reposition the battery for access.
  9. Remove the cowl plenum drain tube from the heater/air conditioning housing stud; it-s located behind the cylinder head on the cowl.
  10. From the bottom of the heater/air conditioning housing, remove the floor duct.
  11. On the passenger side, remove the heater/air conditioning housing-to-plenum bracket screw.
  12. Pull the heater/air conditioning housing down far enough to clear the defrost/demist and fresh air ducts, then, rearward far enough to clear the mounting studs and the evaporator drain tube to clear the dash panel holes.
  13. Remove the heater/air conditioning housing assembly from the vehicle.
  14. Remove the heater/air conditioning housing upper case.
  15. Lift the heater core from the lower half of the heater/air conditioning housing.

    Click image to see an enlarged view

    Fig. View of the instrument panel and fasteners-Jeep Cherokee



    Click image to see an enlarged view

    Fig. Exploded view of the heater core assembly-Jeep Cherokee



    Click image to see an enlarged view

    Fig. View of the heater core-Jeep Cherokee


To install:

  1. Assemble the heater core into the lower half of the heater/air conditioning housing.
  2. Install the heater/air conditioning housing upper case.
  3. Install the heater/air conditioning housing assembly to the vehicle.
  4. On the passenger-s side, install the heater/air conditioning housing-to-plenum bracket screw.
  5. At the bottom of the heater/air conditioning housing, install the floor duct.
  6. Install the cowl plenum drain tube to the heater/air conditioning housing stud; it-s located behind the cylinder head on the cowl.
  7. In the engine compartment, install the 5 heater/air conditioning housing-to-chassis nuts.
  8. Connect the heater/air conditioning system vacuum supply line connector to the T-fitting near the heater core tubes.
  9. Connect the heater hoses to the heater core tubes.
  10. Connect the refrigerant lines to the evaporator.
  11. If equipped with air conditioning, evacuate and charge the air conditioning system refrigerant.
  12. Install the instrument panel by performing the following procedure:
    1. Using an assistant, install the instrument panel to the vehicle.
    2. Install the 4 upper instrument panel-to-dash nuts.
    3. Install the 3 instrument panel-to-door hinge pillar screws.
    4. Install the upper cover to the instrument panel.
    5. Reaching through the glove box opening, connect the following items.

      Two lower passenger-s side air bag module bracket-to-dash panel nuts.
      Passenger-s side air bag ON/OFF switch wiring harness to the retainer clip on the plenum bracket that supports the heater/air conditioning housing just inboard of the fuse block module.
      Two instrument panel wiring harness connectors to the passenger air bag ON/OFF switch wiring harness connector.
      Two halves of the radio antenna coaxial cable connector.
      Side window demister hose at the heater/air conditioning housing demister/defroster duct (passenger-s side).
      Instrument panel wiring harness connector to the passenger-s side air bag module wiring harness connector.
      Instrument panel wiring harness connector to the heater/air conditioning system wiring harness connector.
      Two halves of the heater/air conditioning system vacuum harness connector.

    6. Install the glove box.
    7. Under the driver-s side of the instrument panel, connect the following items:

      Side window demister hose at the heater/air conditioning housing demister/defroster duct on the driver-s side.
      Instrument panel wiring harness connector to the 100-way wiring harness connector at the left side of the inner panel.

    8. Install the steering column.
    9. Install the knee blocker to the instrument panel.

  13. Connect and remove the negative battery.
  14. Refill the cooling system.
  15. Run the engine to normal operating temperatures; then, check the climate control operation and check for leaks.
Eric and 3 other Jeep Specialists are ready to help you
Hi,

forgot one diagram.

this shows locations of nuts to remove for the hvac housing to pull it from the firewall:

graphic