1991 Ezgo will not move

[boco]

Hello this is my first post on this site. I m looking into buying a friend of mine 1991 ezgo electric golf cart. The other day my son was riding it and it just stop. We got in it the garage to check it out and did not see anything right off. So I charge it over night and start looking again the next morning. I clean all the batteries terminal and check the water level in the batteries everything OK. The solenoid is picking up and the pot is show ohms to the black box (I think this is the speed controller). How can I tell if the controller is working? The friend say he had put on a new controller a couple of years ago because it had been hit by lighting. The amufactures date on the batteries is DEC. 04. Thanks