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Carhelp4u, ASE CERTIFIED TECH
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2003 gmc sonoma: heater..thermostat, but all I get is cold air blowing

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how do i fix a 2003 gmc sonoma problem with the heater that does not heat. I changed the thermostat, but all I get is cold air blowing.
If you let the engine get up to operating temp are you able to verify that both heater core connections at the firewall are getting hot?
Customer: replied 7 years ago.
yes firewall heater hoses are hot
Customer: replied 7 years ago.
compressor is cycling

Ok the first thing I would recommend would be to verify that the fuse labeled HVAC 1. The next item I would be interested in would be the actual electric actuator that moves the door in the hvac box. The problem is that most of the dash needs to be removed to access this point. The actuator itself is located on the passenger upper side of the havc box. This electric actuator is a common failure in this model. We would need to access the actuator to see if the actuator is moving, and also to verify that the heater door is not broken. Here is an overview of what you will need to do to access this actuator. Feel free to contact me with any questions! Good luck!

  • On vehicles equipped with a manual transmission, remove the shift lever.
  • On vehicles equipped with an automatic transmission, perform the following steps:
    2.1. Apply the park brake.
    2.2. Insert the ignition key and turn the ignition switch to the RUN position.
    2.3. Depress the brake pedal and shift the transmission to the 1 position.
    2.4. Turn the ignition switch to the OFF position.

     


    Object Number: 392686  Size: SH

  • Disconnect the battery negative cable.
  • Disable the passenger side SIR system.
  • Remove the left sound insulator.
  • Remove the right instrument panel sound insulator.
  • If the vehicle is equipped with a multiple CD changer located in the center console, remove the center console.
  • Remove the lower sound insulator.
  • Remove the lower left instrument panel mounting bolt.
  • Remove and retain the instrument panel storage compartment.
  • Remove the lower right instrument panel mounting bolt.
    Object Number: 392691  Size: SH

  • Remove and retain the left and right speakers and the speaker grilles.
  • Use a flat-bladed tool to remove the windshield defroster grille. Retain the windshield defroster grille for use on the replacement I/P carrier.
    Object Number: 392690  Size: SH

  • If the vehicle is equipped with a sunload sensor, twist the sunload sensor 1/4 turn counterclockwise in order to detach it from the windshield defroster grille. Retain the sunload sensor for use on the replacement I/P carrier.

    Important: Always disconnect the brown electrical connector from the body control module (BCM) before disconnecting the purple electrical connector from the BCM.

  • Disconnect the brown electrical connector from the BCM.
  • Disconnect the purple electrical connector from the BCM.
  • Remove the knee bolster.
  • Remove and retain the instrument panel cluster.
  • Remove and retain the radio.
  • Remove and retain the HVAC control assembly.
    Object Number: 392681  Size: SH

  • Remove the left and right instrument panel driver knee bolster brackets.
  • Lower the steering column for clearance.
    Object Number: 303370  Size: SH

    Important: Label all of the connections in order to avoid improper installation.

  • Remove the top instrument panel screws.
  • Roll the instrument panel down.
  • Disconnect the electrical connections, as needed.
  • Remove the fastener that retains the radio antenna cable to the instrument panel.
  • Remove the instrument panel from the vehicle.
    Object Number: 424782  Size: SH

  • Disconnect the electrical connector (2).
    Object Number: 404930  Size: SH

  • Remove the air temperature actuator retaining screws.
  • Remove the air temperature actuator from the HVAC module.
  • Carhelp4u and 4 other Chevy Specialists are ready to help you

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