I have a 1999 Mercury Sable GS, I had the alternator and battery replaced yet the car will start and run for only a few minutes and then shuts off and the car has to be jumped off to get it to start again. What could this be?
It sounds to me, like there is a huge power drain on the battery.
Did you replace the alternator, and replace the battery at the same time? If you only replaced the alternator and used the same crappy battery, you may have caused what is known as " Alternator Death" which can occur when a new alternator is forced to charged a dead battery, and exceeds it's power limitations and shorts out the alternator's reostat. Test the Alternator to be sure.