High Pitch Whistle When HVAC Blower Fan is on High and Full Floor Mode - keywords intermittent noise

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in the PI.

Some customer may report a high pitch whistle or air rushing sound when the HVAC system is set to full floor and the blower fan is set on high. Furthermore, the customer may report the noise comes and goes with the fan speed. One possible cause of the noise could be the defogger vent assembly is not completely seated into the HVAC plenum.

If all diagnostic procedures have been exhausted and the noise remains, the defogger vent assembly should be suspected. The following steps will need to be completed to correct the noise.

1. Remove the windshield garnish molding as listed in SI Document ID # 508258.
2. Remove the upper trim pad as listed in SI Document ID # 630216.
3. Remove the side window defogger outlet ducts as displayed in SI Document ID # 858993.
4. With both hands, lift up on the center defogger outlet vent until you hear a small pop or the assembly returns to the seated position.
5. Keep pressure applied to the center defogger outlet vent and follow in downward until you reach a void between the center defogger outlet vent and the HVAC plenum.
6. Install a piece of stiff packing foam that has been cut into wedge approximately 2 1/2 inches thick, by 3 inches long, by 2 inches wide (the protective door foam that is shipped with a new vehicle is ideal) between the center defogger outlet vent and the HVAC plenum on both sides while maintaining upward pressure on the defogger outlet vent assembly.
7. The wedges will keep the center defogger outlet vent in position and provide support once the upper trim pad is re-installed.
8. Reverse the first three steps and test the system to ensure the concern is repaired.

Note: The system should be tested once steps 4, 5 and 6 have been completed to ensure the complaint is corrected and the center defogger outlet vent has not become unseated.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

(2001-2005 Chevrolet Venture) and (2001-2004 Oldsmobile Silhouette) and (2001-2005 Pontiac Montana)