car has been at my tech for noise in a/c blower motor but cool air is coming out. tech cannot find problem but has determined 1) motor is fine and always blows cold air 2) only makes noise at 1-2 clicks above lowest air flow ( noise stops if increase air flow or lower to lowest speed),3) there are no foreign objects in blower motor4) takes up to 20 minutes for noise to start but it always does if at 1-2 clicks above lowest setting. help!!!any suggestions while car is still with tech