HVAC System May Not Change Modes At High Blower Motor Speed (Replace HVAC Mode Valve)

This bulletin is being revised to update the labor operation code in the Warranty Information section. Please discard Corporate Bulletin Number 04-01-38-003 (Section 01 -- HVAC).

Some customers may comment that the HVAC (heater, ventilation and air conditioning) system does not change modes intermittently when the blower motor is operating at high speed. The customer may not notice that the concern is only apparent when the blower motor is operating at high speed.

This concern may be caused by an HVAC mode valve that sticks when the blower motor is operating at high speed.

Early production 2004 Grand Prix vehicles built in February and early March 2003 were produced with a white film material on the mode valve that may stick when the blower motor is operating at high speed. This concern can be easily diagnosed by operating the HVAC system at the highest blower speed and then cycling through all of the HVAC air delivery modes and checking to see if the air flow comes out of the correct air outlets. If the mode valve is sticking and not allowing the air to come out of the correct air outlet, try lowering the blower speed 50% and then recheck the airflow. If the air flow is now coming out the correct outlet for the selected mode, then the mode valve is intermittently sticking at high blower speeds.

A new mode valve went into production in early March 2003. The film on the original mode valve was white. The film on the new mode valve is orange on the inside and black on the outside. To identify an early built vehicle, inspect the build sticker on the driver's door jamb and look for the build date. If the vehicle has a build date of February or March 2003, then the HVAC module must be inspected to determine the module part number.

To inspect the HVAC module, open the instrument panel compartment and then rotate it completely out of the opening in the instrument panel. To remove the glove box door arm, you must squeeze the upper and lower portion of the plastic arm using your thumb and fore finger near the IP opening end. Inspect the right side of the HVAC module and locate the white barcode identification label at the lower right of the air inlet assembly. The HVAC module part number is found in the first string of digits immediately below the DELPHI name in the upper left corner of the label. If the HVAC module part number is either 10335274 or 10343400, a new mode valve, P/N 10325510, must be installed. Three evaporator case screws, P/N 52466167 (sold individually), are also required to complete this repair. Follow the Mode Valve Assembly Replacement procedure (SI Document ID #978108) in the HVAC section of SI. If a new design mode valve is already installed and the mode change concern at high blower speed is still present, then refer to the Diagnostic Starting Point -- Heating, Ventilation and Air Conditioning procedure (SI Document ID #924761) in SI.

For vehicles repaired under warranty, use: