I have a 99 cavalier. Battery light recently came on. Figured on the alternator because it wouldn't start so had it boosted. After running for awhile, it quit. Purchased and installed a new alternator. When starting, battery light remained on but would go out when RPM was at 2500. Drove it for about15 minutes and all the gauges stopped working. Then, it quit. Tries to start but won't. HELP PLZ!!!

 

If battery is good, replace the alternator.