Hi I have a 2003 monte carlo with a 3.8 engine. When I first start the car everything works great. In about 5 minutes the battery light comes on and the voltage gage goes all the way down. I have cleaned the battery connectionschanged the battery and checked the voltage at the battery. When the car is running the voltage at the battery using a dvm is 14v even though the gage says it is not charging so i don't think its the alternater. Any ideas would be welcomed