95 s 10...battery and alternator checks out ok...battery is fully charged and then will not stay charged...it just steadily drains the battery when running.

Most automobile batteries are lead acid which should have a standing voltage of about 12.6V fully charged at 70 degrees F. To test a battery first it must be fully charged. If fully charged a good battery will stay above 9.5V while cranking engine. Most part stores will charge and test batteries, starters and alternators. To be sure your alternator is properly charging start the engine and turn on the headlights and blower fan to add electrical load. Voltage should be over 13.2V at idle and under 15V with a known good battery. If not check the larger wire bolted to the back of the alternator for loose connection and continuity to the battery. If ok check fuses. If all are present and check good most likely the alternator is bad and needs replacement, although it is possible on many modern automobiles to have a powertrain control module (PCM) be the problem as they serve as the voltage regulator. Most late 90s and newer GM and Chrysler do. If all else fails have a professional check it to be sure. Hopefully this will answer the questions of many. Good luck ??.