I have started having alternator problems. This is indicated as the error message "Alternator Workshop" and the battery lamp comes on. The alternator looks fine, belt turning, no noise, no smells & no unexpected heat. Today I took a voltage reading of the battery & noted that when I start the engine the reading does not rise to an expected 13.5v, it drops a little down to 12.1v. This indicates to me that the alternator is not working. The next test I did was to tap/hit the alternator with an adjustable spanner. This had the effect of hearing the engine go under load (whine down) and the battery voltage to jump upto 13.5v. Now charging and the battery lamp on the dash board goes off. To me this suggests that the alternator brushes are coming to the end of their life & need changing out. Is this possible on the Galaxy alternator? Can the brushes be replaced or am I jumping to the wrong conclussions. Thanks for any help.