Place a volt meter across your Alt, disconnect the battery and see for yourself what the voltage jumps to. Often times it will exceed 400 volts. In automotive electrical school (MOPAR) This was the first thing taught to us dealer weanies. DO NOT UNHOOK A BATTERY WHILE THE ENGINE IS RUNNING! I'm glad to hear you have never had a problem. A better way to see if the Alt is working would be to place a screw driver against the rear center, if it sticks the unit is at least somewhat working.