My gf has a 2002 alero 3.4liter and after letting it sit for a week it's has been off and on starting. We had the alternator,starter,and battery all tested and were good. Also the battery when it wasn't starting was reading 10 to 12 volts and after a quick jump it starts just fine. Does anyone know what the issue might be?my friend has cleaned the ground wire today so hopefully that fixes it but I'm just not sure what it may be.
Battery should be around 12.6 volts. Test it again after it has been sitting for a bit (like a day) see if it drops significantly. If so, the battery might not be able to retain a charge anymore and would need to be replaced.
If its draining slowly, you may have a short somewhere causing the drain.