I would check the charging system. But more then likley the battery must have a drain on it. Check buy putting a 12V test lamp between the neg post and ground, after removing the neg cable. Do this with the eng off. If the light lights you have a drain. Now you goota find it. If it don't light then the battery is not holding a charge and should be checked out. Any auto parts place like Pep Boys, or Auto Zone would do this for free. Good Luck     John 90 vanagon gl