If alternator has small, usually round black plastic item on back of alternator about one to one and one half inches in diameter. That is your voltage regulator as well as brush mount and brushes it costs like 20.00 or so. Two screws affix this item and if brushes worn bad just change unit as comes off pretty easy for inspection usually. (with alternator off of car) Kind of a miantenance item anyways and should be checked once in awhile as brushes are a wear item. Should have mentioned this last night but when you quoted everything looked to be functioning my first thought was even with a loose belt everything looks normal with engine running. Thanks to members in previous threads jogging my memory. On older cars everything electical I clean and put some sort of protective coating on contacts prior to reasembling as a habit in my climate. Kind of depends if you want to get your hands dirty but just checked out a car in my garage and it indeed has the borsh external regulator mounted on alternator. Funny one problem have not had is alternators on these cars. But think will heed my own suggestion. Pull all my alternators. Pull and check regulator/brush assemblies and check them as it is pretty easily done. Judging by my cars high or unknown milage actually will be preventitive maintenance in nature. Now have something more to add to my list of getting roundtoit things to do. Nothing like making work for yourself.......