Have Hade to change Alt. 3 times in past 3 months. The Light comes on in Dash and Quits Charging. The first time it went out was Earler this Summer She was running A/C and was on way to Colorado. I replaced it with a Rebuilt Auto Zone Alt. It lasted about 2 months. I just Repalced It agian to today with a Replacement Alt. Went about 40 miles and the Light on dash Came On and it quit working. What is Causing this.