I replaced the two dead batteries on a John Deere tractor just to have them completely drained. I had alternator tested at O'reilly's and it passed. When the rpms reach 1500 the alt indicator light comes on until it drops below that. I've cleaned every wire connector and terminal connector I can see. Multimeter shows 14.8 when running at the battery and the alt. Anyone got any idea because short of throwing on a new alt just to see if that will fix the problem I am at a loss.