GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Blazer - 4WD - RHD 🢒 Engine 🢒 Engine Cooling 🢒 Heater Core Replacement

Removal Procedure

    Object Number: 404147 Size: SH
  1. Drain the engine coolant. Refer to Cooling System Draining and Filling in Engine Cooling.
  2. Remove the instrument panel. Refer to Instrument Panel Carrier Replacement in Instrument Panel, Gages and Console.
  3. Remove the evaporator case assembly. Refer to Air Conditioning Evaporator Core Replacement .
  4. Remove the heater hoses from heater core. Refer to the following procedures:
    5. •  Heater Inlet Hose Replacement
    •  Heater Outlet Hose Replacement
  5. Disconnect the electrical connector from the HVAC vacuum control valve.
  6. Disconnect the electrical connector from the body control module.
  7. Disconnect vacuum source hose from the hose leading to the HVAC vacuum control valve.
  8. Remove the heater case retaining screws.
  9. Remove the heater case assembly from vehicle.
  10. Remove the heater core access cover screws.
  11. Remove the heater core access cover.
  12. Remove the heater core from the heater case.

Installation Procedure

    Object Number: 404147 Size: SH
  1. Install the heater core to the heater case.
  2. Install the heater core access cover to the heater case.

    3. 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.

  3. Install the heater core access cover retaining screws.

    4. Tighten
    Tighten the heater core access cover screws to 1.9 N·m (17 lb in).

  4. Install the heater case to the vehicle.
  5. Install the heater case retaining nuts and bolts.

    6. Tighten
    Tighten the heater case retaining nuts and bolts to 4.5 N·m (40 lb in).

  6. Connect the vacuum source hose to the hose leading to the HVAC vacuum control valve.
  7. Connect the electrical connector to the body control module.
  8. Connect the electrical connector to the HVAC vacuum control valve.
  9. Install the heater hoses to the heater core. Refer to the following procedures:
    10. •  Heater Inlet Hose Replacement
    •  Heater Outlet Hose Replacement
  10. Install the evaporator case assembly. Refer to Air Conditioning Evaporator Core Replacement .
  11. Remove the instrument panel. Refer to Instrument Panel Carrier Replacement in Instrument Panel, Gages and Console.
  12. Refill the engine cooling system. Refer to Cooling System Draining and Filling in Engine Cooling.
  13. Check the cooling system for leaks.