I have had the tractor for 4 years. The light would come on when starting and then go out. Nothing in the owners manual. I figured it meant not charging but it is.
WOW! Well I'm surprised the light went out because thats an indicator that there is current being applied to the alternator field. You should also have a small LED on the voltage regulator that mimics the dash light. In this case, if the light is out the alternator isn't charging. In lay terms it could just be referred to as the “key on” light, a reminder that the key switch is on. You may want to check the v-belt tension.