3 times now my wife's '93 940 na has stopped running because the battery was dead (tested at 10.5 to 11 volt). When I jump start it, then test the battery with the car running, it's lower voltage (8.5-10.5). I put the battery on the charger overnight, remove the charger, wait 30 minutes, voltage = 13.2, start the car, voltage = 14.2. The first time it happened, I had the battery checked (new Nov. 2009).The 2nd time it happened, I replaced the brushes in the Denso alternator with some used ones from another alternator (new ones still on order), after re-charging the battery, I checked the battery voltage every day for 5 days and it was always 12.6 after sitting overnight. Then last night it happened again. Any ideas on how to solve this? When the battery gets so low it won't run the car, does the alternator stop charging? The car has a new crank pulley so I don't think that's slipping. Thanks.
Marlin