It's under the dash on the right side below the glove box. Here are the directions for removal and replacement. I'm adding them in case you need them. The attached pics correlate with the directions.
2005 Buick LeSabre V6-3.8L VIN K
Vehicle Heating and Air Conditioning Blower Motor Service and Repair Procedures
BLOWER MOTOR REPLACEMENT
1. Remove the right side sound insulator.
2. Disconnect the electrical connector (1) from the blower motor.
3. Disconnect the blower ventilation tube (2) from the module.
4. Remove the blower motor screws (1).
5. Remove the blower motor from the housing.
1. Install the blower motor into the housing.
NOTE: Refer to Fastener Notice in Service Precautions.
2. Install the blower motor screws (1).
Tighten the screws to 1.7 N.M (15 lb in).
3. Install the blower ventilation tube (2) to the module.
4. Connect the blower motor electrical connector (1).
5. Install the right side sound insulator.
I hope this helps. Let me know if you have other questions.
Images (Click to enlarge)
Wednesday, June 24th, 2020 AT 10:04 PM