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Here is information to help you.
Heater/Vent Module Replacement
Important: Mark and use the same mounting bolt for the heater/vent module during the installation process. Other mounting bolts are longer and will obstruct the operation of the temperature door.
Important: The heat/vent mounting stud has a flange on the inside and cannot be removed from under the hood. Stop turning the stud after the threads are off the heat/vent module.
Instrument Panel Carrier Replacement
Disconnect battery cables
Important: Always disconnect the brown electrical connector from the body control module (BCM) before disconnecting the purple electrical connector from the BCM.
Important: Label all of the connections in order to avoid improper installation.
Heater Core Replacement
Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
Tighten Tighten the heater core access cover screws to 1.9 N·m (17 lb in).
Remove the dash completely & then remove the HVAC case. Then remove the heater core.
easier said then done. detail doesn't show clearly how to remove all bolts on the hvac module
Try & move the module & determine if there is a hidden bolt ,this sometimes happens.
Make double sure that all connections to this module are disconnected.