I don't spend a lot of time driving my Merc. She sits for months with no issues when it's time to turn that key. Recently I have noticed the battery dead or extremely weak and after a full charge (Motorcraft Maxx BXT 65-750) the battery tested ok. Took the car to work Friday and drove home without incident. Noticed last night with headlights and A/C the voltage drops to 10 with brake application at idle. The system reads 13.8 - 14.1 at idle with NO load (13.8 - 14.4 is norm). I am gonna remove the alternator and have it tested. I noticed the pulley clutch is locked and spins the stator in both directions. Is there a possibility the clutch may be slipping in the drive direction? I am familiar with the way these work but can they fail and allow slippage under load? I am having the alternator rebuilt and the clutch replaced but with 49K miles an alternator failure seems unlikely. Any opinions on this?