I have a split A/C unit. The heat pump ~6-7 years old, the blower unit in the attic is ~20 years old. I live in No. Cal. and in the summer it gets in the low 100's here. When it is hot out side the A/C works great blowing out cold air. But when it is cooler outside (80-90) the A/C blows luke ware air. Any suggestions? Is it time for a new unit?