Wait until blower is not working. Turn off engine but leave key in position 2 which energizes the blower motor regulator. Remove blower motor cover (six screws on right side of engine) remove filter. You will have access to blower cage. Spin it slightly clockwise with the tip of screwdriver...it will likely spin. Indicating a dead spot on the armature or stuck bearing. You likely need a replacement motor...they do fail and are sold on line at Autohauz for a good price.
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