GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 Sonoma Pickup - 2WD 🢒 Bulletins 🢒 SMU - Revised Heater/Vent Module Replacement

SMU - Revised Heater/Vent Module Replacement

Subject:Revised Heater/Vent Module Replacement

Models:1998-2002 Chevrolet Blazer, S-10
1998-2002 GMC Jimmy, Sonoma
1998-2002 Oldsmobile Bravada


This bulletin is being issued to revise the Heater/Vent Module Replacement procedure in the Heating, Ventilation and Air Conditioning sub-section of the Service Manual. Please replace the current information in the Service Manual with the following information.

The following information has been updated within SI. If you are using a paper version of this Service Manual, please make a reference to this bulletin on the affected page.

Removal Procedure


    Object Number: 617612 Size: SH
  1. Remove the instrument panel. Refer to Instrument Panel (I/P) Carrier Replacement in Instrument Panel, Gages and Console.
  2. Drain the engine coolant. Refer to Draining and Filling Cooling System in Engine Cooling.

    3. Object Number: 617623 Size: SH
  3. Remove the blower motor resistor. Refer to Blower Motor Resistor Assembly Replacement.

    4. 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.

  4. Remove the heat/vent module mounting bolt through the blower motor resistor or service access cover opening.

    5. Object Number: 1595 Size: SH
  5. Remove the right wheel house panel. Refer to Wheelhouse Panel Replacement in Body Front End.
  6. Remove the front right tire. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.
  7. On the Utility only, remove the A/C evaporator and blower module heat shield screws.
  8. On the Utility only, slide the A/C evaporator and blower module heat shield toward the front of the vehicle.
  9. Remove the 2 lower heat/vent module mounting nuts.
  10. On the Utility only, remove the A/C evaporator and blower module heat shield bracket.
  11. Remove the bottom right heat/vent module mounting bolt from inside the vehicle.

    12. 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.

  12. On the Utility only, while an assistant inside the vehicle pulls the bottom right corner of the heat/vent module approximately 2.5 mm (1 in) back, remove the 2 heat/vent module mounting studs.
  13. Lower the vehicle.

    14. Object Number: 529580 Size: SH
  14. On vehicles with a 2.2 L engine only, remove the engine wiring harness bracket located at the rear of the intake manifold. Refer to Valve Rocker Arm Cover Replacement in Engine Mechanical - 2.2 L.
  15. Remove the HVAC module mounting bolt located at the lower left side of the heater core to heater hose connection.
  16. Remove the HVAC module mounting nut located at the lower right side of the heater core to heater connection.

    17. 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.

  17. On the Utility only, loosen the HVAC module mounting studs until the threads are free from the heat/vent module.
  18. Disconnect all of the electrical connectors from the HVAC module.
  19. Disconnect all of the vacuum lines from the heater assembly.
  20. Disconnect the heater hoses from the heater core.
  21. Remove the HVAC module from the vehicle.

Installation Procedure


    Object Number: 529580 Size: SH
  1. If replacing the HVAC module, transfer the components from the old heat/vent module as necessary.

    2. Important: Before installing the HVAC module to the vehicle, ensure that the HVAC module mounting studs are located in the proper positions.

  2. Install the HVAC module to the vehicle.
  3. Connect the heater hoses to the heater core.
  4. Connect all of the vacuum lines to the heater assembly.
  5. Connect all of the electrical connectors to the HVAC module.
  6. Install the bottom right HVAC module mounting bolt from inside the vehicle approximately halfway into the threads.

    7. Notice: Refer to Fastener Notice in Cautions and Notices.

  7. On the Utility only, install the HVAC module mounting stud located at the lower right side of the heater core to heater hoses connection in the engine compartment.

    8. Tighten
    Tighten the HVAC module mounting stud to 4.5 N·m (40 lb in).

  8. Raise the vehicle.
  9. On the Utility only, install the bottom right HVAC mounting studs. Ask an assistant to pull the bottom right corner of the HVAC module back from inside the vehicle.

    10. Tighten
    Tighten the heat/vent module mounting studs to 4.5 N·m (40 lb in).

  10. On the Utility only, install the A/C evaporator and blower module heat shield bracket.
  11. Install the heater/vent module mounting nuts.

    12. Tighten
    Tighten the HVAC module mounting nuts to 4.5 N·m (40 lb in).

  12. On the Utility only, slide the A/C evaporator and blower module heat shield into the original position.
  13. On the Utility only, install the A/C evaporator and blower module heat shield screws.

    14. Tighten
    Tighten the A/C evaporator and blower module heat shield screws 2.2 N·m (19 lb in).


    Object Number: 1595 Size: SH
  14. Install the right front tire. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.
  15. Install the bottom right HVAC module mounting bolt from inside the vehicle.

    16. Tighten
    Tighten the HVAC module mounting bolt to 4.5 N·m (40 lb in).

  16. Install the right wheel house panel. Refer to Wheelhouse Panel Replacement in Body Front End.

    17. Object Number: 529580 Size: SH
  17. Install the HVAC module mounting nut located at the lower right side of the heater core to heater connection.

    18. Tighten
    Tighten the HVAC module mounting nut to 4.5 N·m (40 lb in).

  18. Install the HVAC module mounting bolt located at the lower left side of the heater core to heater hose connection.

    19. Tighten
    Tighten the HVAC module mounting bolt to 4.5 N·m (40 lb in).

  19. On vehicles with the 2.2 L engine only, install the engine wiring harness bracket located at the rear of the intake manifold. Refer to Valve Rocker Arm Cover Replacement in Engine Mechanical - 2.2 L.

    20. Important: Use the same mounting bolt marked during removal for the HVAC module during the installation process. Other mounting bolts are longer and will obstruct the operation of the temperature door.

  20. Install the HVAC module mounting bolt through the blower motor resistor or service access cover opening.

    21. Tighten
    Tighten the HVAC module mounting bolt to 4.5 N·m (40 lb in).


    Object Number: 617623 Size: SH
  21. Install the blower motor resistor. Refer to Blower Motor Resistor Assembly Replacement.
  22. Refill the engine coolant. Refer to Draining and Filling Cooling System in Engine Cooling.
  23. Install the instrument panel. Refer to Instrument Panel (I/P) Carrier Replacement in Instrument Panel, Gages and Console.